upstream status: https://github.com/dart-lang/sdk/issues/51535
diff --git a/third_party/zlib/BUILD.gn b/third_party/zlib/BUILD.gn
index 3a71693..ce9fb5c 100644
--- a/third_party/zlib/BUILD.gn
+++ b/third_party/zlib/BUILD.gn
@@ -1,8 +1,9 @@
-# Copyright (c) 2013 The Chromium Authors. All rights reserved.
+# Copyright 2013 The Chromium Authors
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/compiler/compiler.gni")
+import("system.gni")
 
 if (build_with_chromium) {
   import("//testing/test.gni")
@@ -12,417 +13,471 @@ if (current_cpu == "arm" || current_cpu == "arm64") {
   import("//build/config/arm.gni")
 }
 
-config("zlib_config") {
-  include_dirs = [ "." ]
+if (use_system_zlib) {
+  import("//build/shim_headers.gni")
 }
 
-config("zlib_internal_config") {
-  defines = [ "ZLIB_IMPLEMENTATION" ]
-
-  if (!is_debug) {
-    # Build code using -O3, see: crbug.com/1084371.
-    configs = [ "//build/config/compiler:optimize_speed" ]
-  }
-  if (is_debug || use_libfuzzer) {
-    # Enable zlib's asserts in debug and fuzzer builds.
-    defines += [ "ZLIB_DEBUG" ]
-  }
-
-  if (is_win && !is_clang) {
-    # V8 supports building with msvc, these silence some warnings that
-    # causes compilation to fail (https://crbug.com/1255096).
-    cflags = [
-      "/wd4244",
-      "/wd4100",
-      "/wd4702",
-      "/wd4127",
-    ]
-  }
-}
-
-source_set("zlib_common_headers") {
-  sources = [
-    "chromeconf.h",
-    "deflate.h",
-    "inffast.h",
-    "inffixed.h",
-    "inflate.h",
-    "inftrees.h",
-    "zconf.h",
-    "zlib.h",
-    "zutil.h",
-  ]
+config("system_zlib") {
+  defines = [ "USE_SYSTEM_ZLIB=1" ]
 }
 
-use_arm_neon_optimizations = false
-if ((current_cpu == "arm" || current_cpu == "arm64") &&
-    !(is_win && !is_clang)) {
-  # TODO(richard.townsend@arm.com): Optimizations temporarily disabled for
-  # Windows on Arm MSVC builds, see http://crbug.com/v8/10012.
-  if (arm_use_neon) {
-    use_arm_neon_optimizations = true
+config("zlib_config") {
+  if (use_system_zlib) {
+    configs = [ ":system_zlib" ]
+  } else {
+    include_dirs = [ "." ]
   }
 }
 
-use_x86_x64_optimizations =
-    (current_cpu == "x86" || current_cpu == "x64") && !is_ios
+if (!use_system_zlib) {
+  config("zlib_internal_config") {
+    defines = [ "ZLIB_IMPLEMENTATION" ]
 
-config("zlib_adler32_simd_config") {
-  if (use_x86_x64_optimizations) {
-    defines = [ "ADLER32_SIMD_SSSE3" ]
-    if (is_win) {
-      defines += [ "X86_WINDOWS" ]
-    } else {
-      defines += [ "X86_NOT_WINDOWS" ]
+    if (!is_debug) {
+      # Build code using -O3, see: crbug.com/1084371.
+      configs = [ "//build/config/compiler:optimize_speed" ]
+    }
+    if (is_debug || use_libfuzzer) {
+      # Enable zlib's asserts in debug and fuzzer builds.
+      defines += [ "ZLIB_DEBUG" ]
     }
-  }
 
-  if (use_arm_neon_optimizations) {
-    defines = [ "ADLER32_SIMD_NEON" ]
+    if (is_win && !is_clang) {
+      # V8 supports building with msvc, these silence some warnings that
+      # causes compilation to fail (https://crbug.com/1255096).
+      cflags = [
+        "/wd4244",
+        "/wd4100",
+        "/wd4702",
+        "/wd4127",
+      ]
+    }
   }
-}
 
-source_set("zlib_adler32_simd") {
-  visibility = [ ":*" ]
+  source_set("zlib_common_headers") {
+    visibility = [ ":*" ]
 
-  if (use_x86_x64_optimizations) {
     sources = [
-      "adler32_simd.c",
-      "adler32_simd.h",
+      "chromeconf.h",
+      "deflate.h",
+      "inffast.h",
+      "inffixed.h",
+      "inflate.h",
+      "inftrees.h",
+      "zconf.h",
+      "zlib.h",
+      "zutil.h",
     ]
-
-    if (!is_win || is_clang) {
-      cflags = [ "-mssse3" ]
-    }
   }
 
-  if (use_arm_neon_optimizations) {
-    sources = [
-      "adler32_simd.c",
-      "adler32_simd.h",
-    ]
+  use_arm_neon_optimizations = false
+  if ((current_cpu == "arm" || current_cpu == "arm64") &&
+      !(is_win && !is_clang)) {
+    # TODO(richard.townsend@arm.com): Optimizations temporarily disabled for
+    # Windows on Arm MSVC builds, see http://crbug.com/v8/10012.
+    if (arm_use_neon) {
+      use_arm_neon_optimizations = true
+    }
   }
 
-  configs += [ ":zlib_internal_config" ]
+  use_x86_x64_optimizations =
+      (current_cpu == "x86" || current_cpu == "x64") && !is_ios
 
-  public_configs = [ ":zlib_adler32_simd_config" ]
-
-  public_deps = [ ":zlib_common_headers" ]
-}
-
-if (use_arm_neon_optimizations) {
-  config("zlib_arm_crc32_config") {
-    # Disabled for iPhone, as described in DDI0487C_a_armv8_arm:
-    #  "All implementations of the ARMv8.1 architecture are required to
-    #   implement the CRC32* instructions. These are optional in ARMv8.0."
-    if (!is_ios) {
-      defines = [ "CRC32_ARMV8_CRC32" ]
-      if (is_android) {
-        defines += [ "ARMV8_OS_ANDROID" ]
-      } else if (is_linux || is_chromeos) {
-        defines += [ "ARMV8_OS_LINUX" ]
-      } else if (is_mac) {
-        defines += [ "ARMV8_OS_MACOS" ]
-      } else if (is_fuchsia) {
-        defines += [ "ARMV8_OS_FUCHSIA" ]
-      } else if (is_win) {
-        defines += [ "ARMV8_OS_WINDOWS" ]
+  config("zlib_adler32_simd_config") {
+    if (use_x86_x64_optimizations) {
+      defines = [ "ADLER32_SIMD_SSSE3" ]
+      if (is_win) {
+        defines += [ "X86_WINDOWS" ]
       } else {
-        assert(false, "Unsupported ARM OS")
+        defines += [ "X86_NOT_WINDOWS" ]
       }
     }
+
+    if (use_arm_neon_optimizations) {
+      defines = [ "ADLER32_SIMD_NEON" ]
+    }
   }
 
-  source_set("zlib_arm_crc32") {
+  source_set("zlib_adler32_simd") {
     visibility = [ ":*" ]
 
-    if (!is_ios) {
-      include_dirs = [ "." ]
+    if (use_x86_x64_optimizations) {
+      sources = [
+        "adler32_simd.c",
+        "adler32_simd.h",
+      ]
 
-      if (!is_win && !is_clang) {
-        assert(!use_thin_lto,
-               "ThinLTO fails mixing different module-level targets")
-        cflags_c = [ "-march=armv8-a+crc" ]
+      if (!is_win || is_clang) {
+        cflags = [ "-mssse3" ]
       }
+    }
 
+    if (use_arm_neon_optimizations) {
       sources = [
-        "crc32_simd.c",
-        "crc32_simd.h",
+        "adler32_simd.c",
+        "adler32_simd.h",
       ]
     }
 
     configs += [ ":zlib_internal_config" ]
 
-    public_configs = [ ":zlib_arm_crc32_config" ]
+    public_configs = [ ":zlib_adler32_simd_config" ]
 
     public_deps = [ ":zlib_common_headers" ]
   }
-}
-
-config("zlib_inflate_chunk_simd_config") {
-  if (use_x86_x64_optimizations) {
-    defines = [ "INFLATE_CHUNK_SIMD_SSE2" ]
 
-    if (current_cpu == "x64") {
-      defines += [ "INFLATE_CHUNK_READ_64LE" ]
+  if (use_arm_neon_optimizations) {
+    config("zlib_arm_crc32_config") {
+      # Disabled for iPhone, as described in DDI0487C_a_armv8_arm:
+      #  "All implementations of the ARMv8.1 architecture are required to
+      #   implement the CRC32* instructions. These are optional in ARMv8.0."
+      if (!is_ios) {
+        defines = [ "CRC32_ARMV8_CRC32" ]
+        if (is_android) {
+          defines += [ "ARMV8_OS_ANDROID" ]
+        } else if (is_linux || is_chromeos) {
+          defines += [ "ARMV8_OS_LINUX" ]
+        } else if (is_mac) {
+          defines += [ "ARMV8_OS_MACOS" ]
+        } else if (is_fuchsia) {
+          defines += [ "ARMV8_OS_FUCHSIA" ]
+        } else if (is_win) {
+          defines += [ "ARMV8_OS_WINDOWS" ]
+        } else {
+          assert(false, "Unsupported ARM OS")
+        }
+      }
     }
-  }
 
-  if (use_arm_neon_optimizations) {
-    defines = [ "INFLATE_CHUNK_SIMD_NEON" ]
+    source_set("zlib_arm_crc32") {
+      visibility = [ ":*" ]
 
-    if (current_cpu == "arm64") {
-      defines += [ "INFLATE_CHUNK_READ_64LE" ]
-    }
-  }
-}
+      if (!is_ios) {
+        include_dirs = [ "." ]
 
-source_set("zlib_inflate_chunk_simd") {
-  visibility = [ ":*" ]
+        if (!is_win && !is_clang) {
+          assert(!use_thin_lto,
+                 "ThinLTO fails mixing different module-level targets")
+          cflags_c = [ "-march=armv8-a+aes+crc" ]
+        }
 
-  if (use_x86_x64_optimizations || use_arm_neon_optimizations) {
-    include_dirs = [ "." ]
+        sources = [
+          "crc32_simd.c",
+          "crc32_simd.h",
+        ]
+      }
 
-    sources = [
-      "contrib/optimizations/chunkcopy.h",
-      "contrib/optimizations/inffast_chunk.c",
-      "contrib/optimizations/inffast_chunk.h",
-      "contrib/optimizations/inflate.c",
-    ]
-  }
+      configs += [ ":zlib_internal_config" ]
 
-  configs += [ ":zlib_internal_config" ]
+      public_configs = [ ":zlib_arm_crc32_config" ]
 
-  # Needed for MSVC, which is still supported by V8 and PDFium. zlib uses K&R C
-  # style function declarations, which triggers warning C4131.
-  configs -= [ "//build/config/compiler:chromium_code" ]
-  configs += [ "//build/config/compiler:no_chromium_code" ]
+      public_deps = [ ":zlib_common_headers" ]
+    }
+  }
 
-  public_configs = [ ":zlib_inflate_chunk_simd_config" ]
+  config("zlib_inflate_chunk_simd_config") {
+    if (use_x86_x64_optimizations) {
+      defines = [ "INFLATE_CHUNK_SIMD_SSE2" ]
 
-  public_deps = [ ":zlib_common_headers" ]
-}
+      if (current_cpu == "x64") {
+        defines += [ "INFLATE_CHUNK_READ_64LE" ]
+      }
+    }
+
+    if (use_arm_neon_optimizations) {
+      defines = [ "INFLATE_CHUNK_SIMD_NEON" ]
 
-config("zlib_crc32_simd_config") {
-  if (use_x86_x64_optimizations) {
-    defines = [ "CRC32_SIMD_SSE42_PCLMUL" ]
+      if (current_cpu == "arm64") {
+        defines += [ "INFLATE_CHUNK_READ_64LE" ]
+      }
+    }
   }
-}
 
-source_set("zlib_crc32_simd") {
-  visibility = [ ":*" ]
+  source_set("zlib_inflate_chunk_simd") {
+    visibility = [ ":*" ]
 
-  if (use_x86_x64_optimizations) {
-    sources = [
-      "crc32_simd.c",
-      "crc32_simd.h",
-      "crc_folding.c",
-    ]
+    if (use_x86_x64_optimizations || use_arm_neon_optimizations) {
+      include_dirs = [ "." ]
 
-    if (!is_win || is_clang) {
-      cflags = [
-        "-msse4.2",
-        "-mpclmul",
+      sources = [
+        "contrib/optimizations/chunkcopy.h",
+        "contrib/optimizations/inffast_chunk.c",
+        "contrib/optimizations/inffast_chunk.h",
+        "contrib/optimizations/inflate.c",
       ]
     }
-  }
 
-  configs += [ ":zlib_internal_config" ]
+    configs += [ ":zlib_internal_config" ]
 
-  public_configs = [ ":zlib_crc32_simd_config" ]
+    # Needed for MSVC, which is still supported by V8 and PDFium. zlib uses K&R C
+    # style function declarations, which triggers warning C4131.
+    configs -= [ "//build/config/compiler:chromium_code" ]
+    configs += [ "//build/config/compiler:no_chromium_code" ]
+    configs += [ ":zlib_warnings" ]
 
-  public_deps = [ ":zlib_common_headers" ]
-}
+    public_configs = [ ":zlib_inflate_chunk_simd_config" ]
 
-config("zlib_slide_hash_simd_config") {
-  if (use_x86_x64_optimizations) {
-    defines = [ "DEFLATE_SLIDE_HASH_SSE2" ]
+    public_deps = [ ":zlib_common_headers" ]
   }
 
-  if (use_arm_neon_optimizations) {
-    defines = [ "DEFLATE_SLIDE_HASH_NEON" ]
+  config("zlib_crc32_simd_config") {
+    if (use_x86_x64_optimizations) {
+      defines = [ "CRC32_SIMD_SSE42_PCLMUL" ]
+    }
   }
-}
 
-source_set("zlib_slide_hash_simd") {
-  visibility = [ ":*" ]
+  source_set("zlib_crc32_simd") {
+    visibility = [ ":*" ]
 
-  if (use_x86_x64_optimizations) {
-    sources = [ "slide_hash_simd.h" ]
+    if (use_x86_x64_optimizations) {
+      sources = [
+        "crc32_simd.c",
+        "crc32_simd.h",
+        "crc_folding.c",
+      ]
+
+      if (!is_win || is_clang) {
+        cflags = [
+          "-msse4.2",
+          "-mpclmul",
+        ]
+      }
+    }
+
+    configs += [ ":zlib_internal_config" ]
+
+    public_configs = [ ":zlib_crc32_simd_config" ]
+
+    public_deps = [ ":zlib_common_headers" ]
   }
 
-  if (use_arm_neon_optimizations) {
-    sources = [ "slide_hash_simd.h" ]
+  config("zlib_slide_hash_simd_config") {
+    if (use_x86_x64_optimizations) {
+      defines = [ "DEFLATE_SLIDE_HASH_SSE2" ]
+    }
+
+    if (use_arm_neon_optimizations) {
+      defines = [ "DEFLATE_SLIDE_HASH_NEON" ]
+    }
   }
 
-  configs += [ ":zlib_internal_config" ]
+  source_set("zlib_slide_hash_simd") {
+    visibility = [ ":*" ]
 
-  public_configs = [ ":zlib_slide_hash_simd_config" ]
+    if (use_x86_x64_optimizations) {
+      sources = [ "slide_hash_simd.h" ]
+    }
 
-  public_deps = [ ":zlib_common_headers" ]
-}
+    if (use_arm_neon_optimizations) {
+      sources = [ "slide_hash_simd.h" ]
+    }
 
-config("zlib_warnings") {
-  if (is_clang && use_x86_x64_optimizations) {
-    cflags = [ "-Wno-incompatible-pointer-types" ]
-  }
-}
+    configs += [ ":zlib_internal_config" ]
 
-component("zlib") {
-  if (!is_win) {
-    # Don't stomp on "libzlib" on other platforms.
-    output_name = "chrome_zlib"
-  }
+    public_configs = [ ":zlib_slide_hash_simd_config" ]
 
-  sources = [
-    "adler32.c",
-    "chromeconf.h",
-    "compress.c",
-    "contrib/optimizations/insert_string.h",
-    "cpu_features.c",
-    "cpu_features.h",
-    "crc32.c",
-    "crc32.h",
-    "deflate.c",
-    "deflate.h",
-    "gzclose.c",
-    "gzguts.h",
-    "gzlib.c",
-    "gzread.c",
-    "gzwrite.c",
-    "infback.c",
-    "inffast.c",
-    "inffast.h",
-    "inffixed.h",
-    "inflate.h",
-    "inftrees.c",
-    "inftrees.h",
-    "trees.c",
-    "trees.h",
-    "uncompr.c",
-    "zconf.h",
-    "zlib.h",
-    "zutil.c",
-    "zutil.h",
-  ]
-
-  defines = []
-  deps = []
-
-  if (!use_x86_x64_optimizations && !use_arm_neon_optimizations) {
-    # Apparently android_cronet bot builds with NEON disabled and
-    # we also should disable optimizations for iOS@x86 (a.k.a. simulator).
-    defines += [ "CPU_NO_SIMD" ]
+    public_deps = [ ":zlib_common_headers" ]
   }
 
-  if (is_ios) {
-    # iOS@ARM is a special case where we always have NEON but don't check
-    # for crypto extensions.
-    # TODO(cavalcantii): verify what is the current state of CPU features
-    # shipped on latest iOS devices.
-    defines += [ "ARM_OS_IOS" ]
+  config("zlib_warnings") {
+    if (is_clang) {
+      cflags = [
+        "-Wno-deprecated-non-prototype",
+        "-Wno-incompatible-pointer-types",
+        "-Wunused-variable",
+      ]
+    }
   }
 
-  if (use_x86_x64_optimizations || use_arm_neon_optimizations) {
-    deps += [
-      ":zlib_adler32_simd",
-      ":zlib_inflate_chunk_simd",
-      ":zlib_slide_hash_simd",
+  component("zlib") {
+    if (!is_win) {
+      # Don't stomp on "libzlib" on other platforms.
+      output_name = "chrome_zlib"
+    }
+
+    sources = [
+      "adler32.c",
+      "chromeconf.h",
+      "compress.c",
+      "contrib/optimizations/insert_string.h",
+      "cpu_features.c",
+      "cpu_features.h",
+      "crc32.c",
+      "crc32.h",
+      "deflate.c",
+      "deflate.h",
+      "gzclose.c",
+      "gzguts.h",
+      "gzlib.c",
+      "gzread.c",
+      "gzwrite.c",
+      "infback.c",
+      "inffast.c",
+      "inffast.h",
+      "inffixed.h",
+      "inflate.h",
+      "inftrees.c",
+      "inftrees.h",
+      "trees.c",
+      "trees.h",
+      "uncompr.c",
+      "zconf.h",
+      "zlib.h",
+      "zutil.c",
+      "zutil.h",
     ]
 
-    if (use_x86_x64_optimizations) {
-      deps += [ ":zlib_crc32_simd" ]
-    } else if (use_arm_neon_optimizations) {
-      deps += [ ":zlib_arm_crc32" ]
+    defines = []
+    deps = []
+
+    if (!use_x86_x64_optimizations && !use_arm_neon_optimizations) {
+      # Apparently android_cronet bot builds with NEON disabled and
+      # we also should disable optimizations for iOS@x86 (a.k.a. simulator).
+      defines += [ "CPU_NO_SIMD" ]
     }
-  } else {
-    sources += [ "inflate.c" ]
-  }
 
-  if (is_android) {
-    import("//build/config/android/config.gni")
-    if (defined(android_ndk_root) && android_ndk_root != "") {
-      deps += [ "//third_party/android_ndk:cpu_features" ]
+    if (is_ios) {
+      # iOS@ARM is a special case where we always have NEON but don't check
+      # for crypto extensions.
+      # TODO(cavalcantii): verify what is the current state of CPU features
+      # shipped on latest iOS devices.
+      defines += [ "ARM_OS_IOS" ]
+    }
+
+    if (use_x86_x64_optimizations || use_arm_neon_optimizations) {
+      deps += [
+        ":zlib_adler32_simd",
+        ":zlib_inflate_chunk_simd",
+        ":zlib_slide_hash_simd",
+      ]
+
+      if (use_x86_x64_optimizations) {
+        deps += [ ":zlib_crc32_simd" ]
+      } else if (use_arm_neon_optimizations) {
+        deps += [ ":zlib_arm_crc32" ]
+      }
     } else {
-      assert(false, "CPU detection requires the Android NDK")
+      sources += [ "inflate.c" ]
     }
-  }
 
-  configs -= [ "//build/config/compiler:chromium_code" ]
-  configs += [ "//build/config/compiler:no_chromium_code" ]
+    if (is_android) {
+      import("//build/config/android/config.gni")
+      if (defined(android_ndk_root) && android_ndk_root != "") {
+        deps += [ "//third_party/android_ndk:cpu_features" ]
+      } else {
+        assert(false, "CPU detection requires the Android NDK")
+      }
+    }
+
+    configs -= [ "//build/config/compiler:chromium_code" ]
+    configs += [ "//build/config/compiler:no_chromium_code" ]
 
-  public_configs = [ ":zlib_config" ]
+    public_configs = [ ":zlib_config" ]
 
-  configs += [
-    ":zlib_internal_config",
+    configs += [
+      ":zlib_internal_config",
 
-    # Must be after no_chromium_code for warning flags to be ordered correctly.
-    ":zlib_warnings",
-  ]
+      # Must be after no_chromium_code for warning flags to be ordered correctly.
+      ":zlib_warnings",
+    ]
 
-  allow_circular_includes_from = deps
+    allow_circular_includes_from = deps
+  }
+} else {
+  shim_headers("zlib_shim") {
+    root_path = "//zlib"
+    headers = [ "zlib.h" ]
+  }
+  source_set("zlib") {
+    deps = [ ":zlib_shim" ]
+    libs = [ "z" ]
+    public_configs = [ ":system_zlib" ]
+  }
 }
 
-config("minizip_warnings") {
-  visibility = [ ":*" ]
+if (!use_system_zlib) {
+  config("minizip_warnings") {
+    visibility = [ ":*" ]
 
-  if (is_clang) {
-    # zlib uses `if ((a == b))` for some reason.
-    cflags = [ "-Wno-parentheses-equality" ]
+    if (is_clang) {
+      cflags = [
+        # zlib uses `if ((a == b))` for some reason.
+        "-Wno-parentheses-equality",
+        "-Wno-deprecated-non-prototype",
+      ]
+    }
   }
-}
 
-static_library("minizip") {
-  sources = [
-    "contrib/minizip/ioapi.c",
-    "contrib/minizip/ioapi.h",
-    "contrib/minizip/iowin32.c",
-    "contrib/minizip/iowin32.h",
-    "contrib/minizip/unzip.c",
-    "contrib/minizip/unzip.h",
-    "contrib/minizip/zip.c",
-    "contrib/minizip/zip.h",
-  ]
-
-  if (!is_win) {
-    sources -= [
+  static_library("minizip") {
+    sources = [
+      "contrib/minizip/ioapi.c",
+      "contrib/minizip/ioapi.h",
       "contrib/minizip/iowin32.c",
       "contrib/minizip/iowin32.h",
+      "contrib/minizip/unzip.c",
+      "contrib/minizip/unzip.h",
+      "contrib/minizip/zip.c",
+      "contrib/minizip/zip.h",
     ]
-  }
 
-  if (is_apple || is_android || is_nacl) {
-    # Mac, Android and the BSDs don't have fopen64, ftello64, or fseeko64. We
-    # use fopen, ftell, and fseek instead on these systems.
-    defines = [ "USE_FILE32API" ]
-  }
+    if (!is_win) {
+      sources -= [
+        "contrib/minizip/iowin32.c",
+        "contrib/minizip/iowin32.h",
+      ]
+    }
+
+    if (is_apple || is_android || is_nacl) {
+      # Mac, Android and the BSDs don't have fopen64, ftello64, or fseeko64. We
+      # use fopen, ftell, and fseek instead on these systems.
+      defines = [ "USE_FILE32API" ]
+    }
 
-  deps = [ ":zlib" ]
+    deps = [ ":zlib" ]
 
-  configs -= [ "//build/config/compiler:chromium_code" ]
-  configs += [ "//build/config/compiler:no_chromium_code" ]
+    configs -= [ "//build/config/compiler:chromium_code" ]
+    configs += [ "//build/config/compiler:no_chromium_code" ]
 
-  public_configs = [ ":zlib_config" ]
+    public_configs = [ ":zlib_config" ]
 
-  configs += [
-    # Must be after no_chromium_code for warning flags to be ordered correctly.
-    ":minizip_warnings",
-  ]
+    configs += [
+      # Must be after no_chromium_code for warning flags to be ordered correctly.
+      ":minizip_warnings",
+    ]
+  }
+} else {
+  shim_headers("minizip_shim") {
+    root_path = "contrib"
+    headers = [
+      "minizip/crypt.h",
+      "minizip/ioapi.h",
+      "minizip/iowin32.h",
+      "minizip/mztools.h",
+      "minizip/unzip.h",
+      "minizip/zip.h",
+    ]
+  }
+  source_set("minizip") {
+    deps = [ ":minizip_shim" ]
+    libs = [ "minizip" ]
+  }
 }
 
-executable("zlib_bench") {
-  include_dirs = [ "." ]
+if (!use_system_zlib) {
+  executable("zlib_bench") {
+    include_dirs = [ "." ]
 
-  sources = [ "contrib/bench/zlib_bench.cc" ]
-  if (!is_debug) {
-    configs -= [ "//build/config/compiler:default_optimization" ]
-    configs += [ "//build/config/compiler:optimize_speed" ]
-  }
+    sources = [ "contrib/bench/zlib_bench.cc" ]
+    if (!is_debug) {
+      configs -= [ "//build/config/compiler:default_optimization" ]
+      configs += [ "//build/config/compiler:optimize_speed" ]
+    }
 
-  deps = [ ":zlib" ]
+    deps = [ ":zlib" ]
 
-  configs -= [ "//build/config/compiler:chromium_code" ]
-  configs += [ "//build/config/compiler:no_chromium_code" ]
+    configs -= [ "//build/config/compiler:chromium_code" ]
+    configs += [ "//build/config/compiler:no_chromium_code" ]
+  }
 }
 
 if (!is_win || target_os != "winuwp") {
@@ -432,7 +487,11 @@ if (!is_win || target_os != "winuwp") {
     sources = [ "contrib/minizip/minizip.c" ]
 
     if (is_clang) {
-      cflags = [ "-Wno-incompatible-pointer-types-discards-qualifiers" ]
+      cflags = [
+        "-Wno-incompatible-pointer-types-discards-qualifiers",
+
+        "-Wno-deprecated-non-prototype",
+      ]
     }
 
     if (!is_debug) {
@@ -452,7 +511,10 @@ if (!is_win || target_os != "winuwp") {
     sources = [ "contrib/minizip/miniunz.c" ]
 
     if (is_clang) {
-      cflags = [ "-Wno-incompatible-pointer-types-discards-qualifiers" ]
+      cflags = [
+        "-Wno-incompatible-pointer-types-discards-qualifiers",
+        "-Wno-deprecated-non-prototype",
+      ]
     }
 
     if (!is_debug) {
diff --git a/third_party/zlib/system.gni b/third_party/zlib/system.gni
new file mode 100644
index 0000000..74604f9
--- /dev/null
+++ b/third_party/zlib/system.gni
@@ -0,0 +1,11 @@
+# Copyright 2023 The Chromium Authors
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Separate file, so unbundle toolchains that replace gn files
+# can replace just this file and override the default
+declare_args() {
+  # If true, find zlib and use as shared libraries.
+  # Useful for Linux distribution repository builds.
+  use_system_zlib = false
+}