mmap V8 snapshot and ICU data file in the android_webview

This makes it possible to mmap the V8 snapshot and ICU data file
directly from the WebView APK.
Doing so makes it possible to remove the android_webview_telemetry_build
flag which in turns means we can build the WebView with the same
set of flags that Chrome on Android uses.

BUG=442338

Review URL: https://codereview.chromium.org/812393002

Cr-Commit-Position: refs/heads/master@{#310765}

21 files changed, 243 insertions, 89 deletions

diff --git a/android_webview/android_webview.gyp b/android_webview/android_webview.gyp
index 3f91264..a14ba0c 100644
--- a/android_webview/android_webview.gyp
+++ b/android_webview/android_webview.gyp
@@ -108,6 +108,7 @@
         '../components/components.gyp:web_contents_delegate_android',
         '../content/content.gyp:content_app_both',
         '../content/content.gyp:content_browser',
+        '../gin/gin.gyp:gin',
         '../gpu/blink/gpu_blink.gyp:gpu_blink',
         '../gpu/command_buffer/command_buffer.gyp:gles2_utils',
         '../gpu/gpu.gyp:command_buffer_service',
@@ -300,25 +301,6 @@
             'shared_resources': 1,
           },
           'includes': [ 'apk/system_webview_apk_common.gypi' ],
-          'copies': [
-            {
-              'destination': '<(PRODUCT_DIR)/android_webview_assets',
-              'files': [],
-              'conditions': [
-                ['icu_use_data_file_flag==1', {
-                  'files': [
-                    '<(PRODUCT_DIR)/icudtl.dat',
-                  ],
-                }],
-                ['v8_use_external_startup_data==1', {
-                  'files': [
-                    '<(PRODUCT_DIR)/natives_blob.bin',
-                    '<(PRODUCT_DIR)/snapshot_blob.bin',
-                  ],
-                }],
-              ],
-            },
-          ],
         },
       ],
      }, {  # android_webview_build==1
diff --git a/android_webview/android_webview_tests.gypi b/android_webview/android_webview_tests.gypi
index 2e1ba0e..10ee545 100644
--- a/android_webview/android_webview_tests.gypi
+++ b/android_webview/android_webview_tests.gypi
@@ -17,11 +17,11 @@
         'java_in_dir': 'test/shell',
         'native_lib_target': 'libstandalonelibwebviewchromium',
         'resource_dir': 'test/shell/res',
-        'extensions_to_not_compress': 'pak',
+        'extensions_to_not_compress': 'pak,dat,bin',
         'extra_native_libs': ['<(SHARED_LIB_DIR)/libdrawgl.>(android_product_extension)'],
         'additional_input_paths': [
-          '<(PRODUCT_DIR)/android_webview_assets/webviewchromium.pak',
-          '<(PRODUCT_DIR)/android_webview_assets/en-US.pak',
+          '<(PRODUCT_DIR)/android_webview_apk/assets/webviewchromium.pak',
+          '<(PRODUCT_DIR)/android_webview_apk/assets/en-US.pak',
           '<(PRODUCT_DIR)/android_webview_apk/assets/asset_file.html',
           '<(PRODUCT_DIR)/android_webview_apk/assets/cookie_test.html',
           '<(PRODUCT_DIR)/android_webview_apk/assets/asset_icon.png',
@@ -58,7 +58,7 @@
             '<(java_in_dir)/assets/full_screen_video_inside_div_test.html',
             '<(java_in_dir)/assets/video.mp4',
           ],
-	  'conditions': [
+          'conditions': [
             ['icu_use_data_file_flag==1', {
               'files': [
                 '<(PRODUCT_DIR)/icudtl.dat',
diff --git a/android_webview/apk/system_webview_apk_common.gypi b/android_webview/apk/system_webview_apk_common.gypi
index 0d19dac..2b24785 100644
--- a/android_webview/apk/system_webview_apk_common.gypi
+++ b/android_webview/apk/system_webview_apk_common.gypi
@@ -16,29 +16,51 @@
     'never_lint': 1,
     'R_package': 'com.android.webview.chromium',
     'R_package_relpath': 'com/android/webview/chromium',
-    'extensions_to_not_compress': 'pak',
-    'asset_location': '<(PRODUCT_DIR)/android_webview_assets',
+    'extensions_to_not_compress': 'pak,bin,dat',
+    'asset_location': '<(INTERMEDIATE_DIR)/assets/',
     # TODO: crbug.com/442348 Update proguard.flags and re-enable.
     'proguard_enabled': 'false',
     'proguard_flags_paths': ['<(DEPTH)/android_webview/apk/java/proguard.flags'],
     # TODO: crbug.com/405035 Find a better solution for WebView .pak files.
     'additional_input_paths': [
-      '<(PRODUCT_DIR)/android_webview_assets/webviewchromium.pak',
-      '<(PRODUCT_DIR)/android_webview_assets/en-US.pak',
+      '<(asset_location)/webviewchromium.pak',
+      '<(asset_location)/en-US.pak',
     ],
     'conditions': [
       ['icu_use_data_file_flag==1', {
         'additional_input_paths': [
-          '<(PRODUCT_DIR)/icudtl.dat',
+          '<(asset_location)/icudtl.dat',
         ],
       }],
       ['v8_use_external_startup_data==1', {
         'additional_input_paths': [
-          '<(PRODUCT_DIR)/natives_blob.bin',
-          '<(PRODUCT_DIR)/snapshot_blob.bin',
+          '<(asset_location)/natives_blob.bin',
+          '<(asset_location)/snapshot_blob.bin',
         ],
       }],
     ],
   },
+  'copies': [
+    {
+      'destination': '<(asset_location)',
+      'files': [
+        '<(PRODUCT_DIR)/android_webview_assets/webviewchromium.pak',
+        '<(PRODUCT_DIR)/android_webview_assets/en-US.pak',
+      ],
+      'conditions': [
+        ['icu_use_data_file_flag==1', {
+          'files': [
+            '<(PRODUCT_DIR)/icudtl.dat',
+          ],
+        }],
+        ['v8_use_external_startup_data==1', {
+          'files': [
+            '<(PRODUCT_DIR)/natives_blob.bin',
+            '<(PRODUCT_DIR)/snapshot_blob.bin',
+          ],
+        }],
+      ],
+    },
+  ],
   'includes': [ '../../build/java_apk.gypi' ],
 }
diff --git a/android_webview/lib/DEPS b/android_webview/lib/DEPS
index ab83088..17b7ba6 100644
--- a/android_webview/lib/DEPS
+++ b/android_webview/lib/DEPS
@@ -2,6 +2,7 @@ include_rules = [
   "+cc/base/switches.h",
   "+components",  # For jni registers.
   "+content/public",
+  "+gin/public",
   "+media/base/media_switches.h",  # For media command line switches.
   "+ui/gl",
 ]
diff --git a/android_webview/lib/main/aw_main_delegate.cc b/android_webview/lib/main/aw_main_delegate.cc
index 2164521..c996cc4 100644
--- a/android_webview/lib/main/aw_main_delegate.cc
+++ b/android_webview/lib/main/aw_main_delegate.cc
@@ -8,6 +8,7 @@
 #include "android_webview/browser/browser_view_renderer.h"
 #include "android_webview/browser/scoped_allow_wait_for_legacy_web_view_api.h"
 #include "android_webview/lib/aw_browser_dependency_factory_impl.h"
+#include "android_webview/native/aw_assets.h"
 #include "android_webview/native/aw_media_url_interceptor.h"
 #include "android_webview/native/aw_quota_manager_bridge_impl.h"
 #include "android_webview/native/aw_web_contents_view_delegate.h"
@@ -16,6 +17,7 @@
 #include "android_webview/renderer/aw_content_renderer_client.h"
 #include "base/command_line.h"
 #include "base/cpu.h"
+#include "base/i18n/icu_util.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
@@ -24,7 +26,9 @@
 #include "content/browser/media/android/browser_media_player_manager.h"
 #include "content/public/browser/browser_main_runner.h"
 #include "content/public/browser/browser_thread.h"
+#include "content/public/common/content_descriptors.h"
 #include "content/public/common/content_switches.h"
+#include "gin/public/isolate_holder.h"
 #include "gpu/command_buffer/client/gl_in_process_context.h"
 #include "gpu/command_buffer/service/gpu_switches.h"
 #include "media/base/media_switches.h"
@@ -81,6 +85,23 @@ bool AwMainDelegate::BasicStartupComplete(int* exit_code) {
   // This is needed for sharing textures across the different GL threads.
   cl->AppendSwitch(switches::kEnableThreadedTextureMailboxes);
 
+  // This is needed to be able to mmap the V8 snapshot and ICU data file
+  // directly from the WebView .apk.
+  // This needs to be here so that it gets to run before the code in
+  // content_main_runner that reads these values tries to do so.
+  // In multi-process mode this code would live in
+  // AwContentBrowserClient::GetAdditionalMappedFilesForChildProcess.
+#ifdef V8_USE_EXTERNAL_STARTUP_DATA
+  CHECK(AwAssets::RegisterAssetWithGlobalDescriptors(
+      kV8NativesDataDescriptor, gin::IsolateHolder::kNativesFileName));
+  CHECK(AwAssets::RegisterAssetWithGlobalDescriptors(
+      kV8SnapshotDataDescriptor, gin::IsolateHolder::kSnapshotFileName));
+#endif
+  // TODO(mkosiba): make this CHECK when the android_webview_build uses an asset
+  // from the .apk too.
+  AwAssets::RegisterAssetWithGlobalDescriptors(
+      kAndroidICUDataDescriptor, base::i18n::kIcuDataFileName);
+
   return false;
 }
 
diff --git a/android_webview/native/aw_assets.cc b/android_webview/native/aw_assets.cc
index 6d5ad72..41f2270 100644
--- a/android_webview/native/aw_assets.cc
+++ b/android_webview/native/aw_assets.cc
@@ -32,6 +32,20 @@ bool OpenAsset(const std::string& filename,
   return *fd != -1;
 }
 
+bool RegisterAssetWithGlobalDescriptors(base::GlobalDescriptors::Key key,
+                                        const std::string& asset_filename) {
+  int asset_fd = 0;
+  int64 asset_off = 0;
+  int64 asset_len = 0;
+  bool result =
+      AwAssets::OpenAsset(asset_filename, &asset_fd, &asset_off, &asset_len);
+  if (result) {
+    base::GlobalDescriptors::GetInstance()->Set(
+        key, asset_fd, base::MemoryMappedFile::Region(asset_off, asset_len));
+  }
+  return result;
+}
+
 }  // namespace AwAssets
 
 bool RegisterAwAssets(JNIEnv* env) {
diff --git a/android_webview/native/aw_assets.h b/android_webview/native/aw_assets.h
index 229392c..16fcafb 100644
--- a/android_webview/native/aw_assets.h
+++ b/android_webview/native/aw_assets.h
@@ -8,6 +8,7 @@
 #include <string>
 
 #include "base/android/jni_android.h"
+#include "base/posix/global_descriptors.h"
 
 namespace android_webview {
 namespace AwAssets {
@@ -23,6 +24,9 @@ bool OpenAsset(const std::string& filename,
                int64* offset,
                int64* size);
 
+bool RegisterAssetWithGlobalDescriptors(base::GlobalDescriptors::Key key,
+                                        const std::string& asset_filename);
+
 }  // namespace AwAssets
 
 bool RegisterAwAssets(JNIEnv* env);
diff --git a/base/files/memory_mapped_file.cc b/base/files/memory_mapped_file.cc
index 745a5ff..891fcff 100644
--- a/base/files/memory_mapped_file.cc
+++ b/base/files/memory_mapped_file.cc
@@ -31,6 +31,7 @@ MemoryMappedFile::~MemoryMappedFile() {
   CloseHandles();
 }
 
+#if !defined(OS_NACL)
 bool MemoryMappedFile::Initialize(const FilePath& file_name) {
   if (IsValid())
     return false;
@@ -85,5 +86,6 @@ void MemoryMappedFile::CalculateVMAlignedBoundaries(int64 start,
   *aligned_start = start & ~mask;
   *aligned_size = (size + *offset + mask) & ~mask;
 }
+#endif
 
 }  // namespace base
diff --git a/base/files/memory_mapped_file_posix.cc b/base/files/memory_mapped_file_posix.cc
index ebf38779..168da92 100644
--- a/base/files/memory_mapped_file_posix.cc
+++ b/base/files/memory_mapped_file_posix.cc
@@ -16,6 +16,7 @@ namespace base {
 MemoryMappedFile::MemoryMappedFile() : data_(NULL), length_(0) {
 }
 
+#if !defined(OS_NACL)
 bool MemoryMappedFile::MapFileRegionToMemory(
     const MemoryMappedFile::Region& region) {
   ThreadRestrictions::AssertIOAllowed();
@@ -74,6 +75,7 @@ bool MemoryMappedFile::MapFileRegionToMemory(
   data_ += data_offset;
   return true;
 }
+#endif
 
 void MemoryMappedFile::CloseHandles() {
   ThreadRestrictions::AssertIOAllowed();
diff --git a/base/i18n/icu_util.cc b/base/i18n/icu_util.cc
index e0bd62c..f1fdda7 100644
--- a/base/i18n/icu_util.cc
+++ b/base/i18n/icu_util.cc
@@ -27,21 +27,21 @@
 #define ICU_UTIL_DATA_SHARED 1
 #define ICU_UTIL_DATA_STATIC 2
 
-#if ICU_UTIL_DATA_IMPL == ICU_UTIL_DATA_FILE
+namespace base {
+namespace i18n {
+
 // Use an unversioned file name to simplify a icu version update down the road.
 // No need to change the filename in multiple places (gyp files, windows
 // build pkg configurations, etc). 'l' stands for Little Endian.
-#define ICU_UTIL_DATA_FILE_NAME "icudtl.dat"
-#elif ICU_UTIL_DATA_IMPL == ICU_UTIL_DATA_SHARED
+// This variable is exported through the header file.
+const char kIcuDataFileName[] = "icudtl.dat";
+#if ICU_UTIL_DATA_IMPL == ICU_UTIL_DATA_SHARED
 #define ICU_UTIL_DATA_SYMBOL "icudt" U_ICU_VERSION_SHORT "_dat"
 #if defined(OS_WIN)
 #define ICU_UTIL_DATA_SHARED_MODULE_NAME "icudt.dll"
 #endif
 #endif
 
-namespace base {
-namespace i18n {
-
 namespace {
 
 #if !defined(NDEBUG)
@@ -53,9 +53,10 @@ bool g_check_called_once = true;
 #endif
 }
 
-
 #if defined(OS_ANDROID)
-bool InitializeICUWithFileDescriptor(int data_fd) {
+bool InitializeICUWithFileDescriptor(
+    int data_fd,
+    base::MemoryMappedFile::Region data_region) {
 #if !defined(NDEBUG)
   DCHECK(!g_check_called_once || !g_called_once);
   g_called_once = true;
@@ -67,7 +68,7 @@ bool InitializeICUWithFileDescriptor(int data_fd) {
 #elif (ICU_UTIL_DATA_IMPL == ICU_UTIL_DATA_FILE)
   CR_DEFINE_STATIC_LOCAL(base::MemoryMappedFile, mapped_file, ());
   if (!mapped_file.IsValid()) {
-    if (!mapped_file.Initialize(base::File(data_fd))) {
+    if (!mapped_file.Initialize(base::File(data_fd), data_region)) {
       LOG(ERROR) << "Couldn't mmap icu data file";
       return false;
     }
@@ -135,13 +136,15 @@ bool InitializeICU() {
     bool path_ok = PathService::Get(base::DIR_EXE, &data_path);
 #endif
     DCHECK(path_ok);
-    data_path = data_path.AppendASCII(ICU_UTIL_DATA_FILE_NAME);
+    data_path = data_path.AppendASCII(kIcuDataFileName);
 #else
     // Assume it is in the framework bundle's Resources directory.
+    base::ScopedCFTypeRef<CFStringRef> data_file_name(
+        SysUTF8ToCFStringRef(kIcuDataFileName));
     FilePath data_path =
-      base::mac::PathForFrameworkBundleResource(CFSTR(ICU_UTIL_DATA_FILE_NAME));
+      base::mac::PathForFrameworkBundleResource(data_file_name);
     if (data_path.empty()) {
-      LOG(ERROR) << ICU_UTIL_DATA_FILE_NAME << " not found in bundle";
+      LOG(ERROR) << kIcuDataFileName << " not found in bundle";
       return false;
     }
 #endif  // OS check
diff --git a/base/i18n/icu_util.h b/base/i18n/icu_util.h
index b0a5dbc..5094cb0 100644
--- a/base/i18n/icu_util.h
+++ b/base/i18n/icu_util.h
@@ -5,12 +5,15 @@
 #ifndef BASE_I18N_ICU_UTIL_H_
 #define BASE_I18N_ICU_UTIL_H_
 
-#include "build/build_config.h"
+#include "base/files/memory_mapped_file.h"
 #include "base/i18n/base_i18n_export.h"
+#include "build/build_config.h"
 
 namespace base {
 namespace i18n {
 
+BASE_I18N_EXPORT extern const char kIcuDataFileName[];
+
 // Call this function to load ICU's data tables for the current process.  This
 // function should be called before ICU is used.
 BASE_I18N_EXPORT bool InitializeICU();
@@ -18,7 +21,9 @@ BASE_I18N_EXPORT bool InitializeICU();
 #if defined(OS_ANDROID)
 // Android uses a file descriptor passed by browser process to initialize ICU
 // in render processes.
-BASE_I18N_EXPORT bool InitializeICUWithFileDescriptor(int data_fd);
+BASE_I18N_EXPORT bool InitializeICUWithFileDescriptor(
+    int data_fd,
+    base::MemoryMappedFile::Region data_region);
 #endif
 
 // In a test binary, the call above might occur twice.
diff --git a/base/posix/global_descriptors.cc b/base/posix/global_descriptors.cc
index bcca443..6c18783 100644
--- a/base/posix/global_descriptors.cc
+++ b/base/posix/global_descriptors.cc
@@ -11,6 +11,16 @@
 
 namespace base {
 
+GlobalDescriptors::Descriptor::Descriptor(Key key, int fd)
+    : key(key), fd(fd), region(base::MemoryMappedFile::Region::kWholeFile) {
+}
+
+GlobalDescriptors::Descriptor::Descriptor(Key key,
+                                          int fd,
+                                          base::MemoryMappedFile::Region region)
+    : key(key), fd(fd), region(region) {
+}
+
 // static
 GlobalDescriptors* GlobalDescriptors::GetInstance() {
   typedef Singleton<base::GlobalDescriptors,
@@ -30,23 +40,38 @@ int GlobalDescriptors::Get(Key key) const {
 int GlobalDescriptors::MaybeGet(Key key) const {
   for (Mapping::const_iterator
        i = descriptors_.begin(); i != descriptors_.end(); ++i) {
-    if (i->first == key)
-      return i->second;
+    if (i->key == key)
+      return i->fd;
   }
 
   return -1;
 }
 
 void GlobalDescriptors::Set(Key key, int fd) {
-  for (Mapping::iterator
-       i = descriptors_.begin(); i != descriptors_.end(); ++i) {
-    if (i->first == key) {
-      i->second = fd;
+  Set(key, fd, base::MemoryMappedFile::Region::kWholeFile);
+}
+
+void GlobalDescriptors::Set(Key key,
+                            int fd,
+                            base::MemoryMappedFile::Region region) {
+  for (auto& i : descriptors_) {
+    if (i.key == key) {
+      i.fd = fd;
+      i.region = region;
       return;
     }
   }
 
-  descriptors_.push_back(std::make_pair(key, fd));
+  descriptors_.push_back(Descriptor(key, fd, region));
+}
+
+base::MemoryMappedFile::Region GlobalDescriptors::GetRegion(Key key) const {
+  for (const auto& i : descriptors_) {
+    if (i.key == key)
+      return i.region;
+  }
+  DLOG(FATAL) << "Unknown global descriptor: " << key;
+  return base::MemoryMappedFile::Region::kWholeFile;
 }
 
 void GlobalDescriptors::Reset(const Mapping& mapping) {
diff --git a/base/posix/global_descriptors.h b/base/posix/global_descriptors.h
index 3d7369c31..c774634 100644
--- a/base/posix/global_descriptors.h
+++ b/base/posix/global_descriptors.h
@@ -12,6 +12,7 @@
 
 #include <stdint.h>
 
+#include "base/files/memory_mapped_file.h"
 #include "base/memory/singleton.h"
 
 namespace base {
@@ -36,8 +37,18 @@ namespace base {
 class BASE_EXPORT GlobalDescriptors {
  public:
   typedef uint32_t Key;
-  typedef std::pair<Key, int> KeyFDPair;
-  typedef std::vector<KeyFDPair> Mapping;
+  struct Descriptor {
+    Descriptor(Key key, int fd);
+    Descriptor(Key key, int fd, base::MemoryMappedFile::Region region);
+
+    // Globally unique key.
+    Key key;
+    // Actual FD.
+    int fd;
+    // Optional region, defaults to kWholeFile.
+    base::MemoryMappedFile::Region region;
+  };
+  typedef std::vector<Descriptor> Mapping;
 
   // Often we want a canonical descriptor for a given Key. In this case, we add
   // the following constant to the key value:
@@ -53,12 +64,19 @@ class BASE_EXPORT GlobalDescriptors {
   // Get a descriptor given a key. It is a fatal error if the key is not known.
   int Get(Key key) const;
 
-  // Get a descriptor give a key. Returns -1 on error.
+  // Get a descriptor given a key. Returns -1 on error.
   int MaybeGet(Key key) const;
 
-  // Set the descriptor for the given key.
+  // Get a region given a key. It is a fatal error if the key is not known.
+  base::MemoryMappedFile::Region GetRegion(Key key) const;
+
+  // Set the descriptor for the given |key|. This sets the region associated
+  // with |key| to kWholeFile.
   void Set(Key key, int fd);
 
+  // Set the descriptor and |region| for the given |key|.
+  void Set(Key key, int fd, base::MemoryMappedFile::Region region);
+
   void Reset(const Mapping& mapping);
 
  private:
diff --git a/build/common.gypi b/build/common.gypi
index 83a3df6..77912bb2 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -161,10 +161,6 @@
         # build system.
         'android_webview_build%': 0,
 
-        # This is set when building the Android WebView in ninja for the
-        # telemetry bot.
-        'android_webview_telemetry_build%': 0,
-
         # Set ARM architecture version.
         'arm_version%': 7,
 
@@ -296,7 +292,6 @@
       'enable_hidpi%': '<(enable_hidpi)',
       'android_channel%': '<(android_channel)',
       'android_webview_build%': '<(android_webview_build)',
-      'android_webview_telemetry_build%': '<(android_webview_telemetry_build)',
       'use_goma%': '<(use_goma)',
       'gomadir%': '<(gomadir)',
       'enable_app_list%': '<(enable_app_list)',
@@ -970,7 +965,7 @@
         # except when building Android WebView.
         # TODO(jshin): Handle 'use_system_icu' on Linux (Chromium).
         # Set the data reduction proxy origin for Android Webview.
-        ['android_webview_build==0 and android_webview_telemetry_build==0', {
+        ['android_webview_build==0', {
           'icu_use_data_file_flag%' : 1,
         }, {
           'icu_use_data_file_flag%' : 0,
@@ -996,7 +991,7 @@
 
         # TODO(baixo): Enable v8_use_external_startup_data
         # http://crbug.com/421063
-        ['android_webview_build==0 and android_webview_telemetry_build==0 and chromecast==0 and chromeos==0 and (OS=="android" or OS=="linux" or OS=="mac")', {
+        ['android_webview_build==0 and chromecast==0 and chromeos==0 and (OS=="android" or OS=="linux" or OS=="mac")', {
           'v8_use_external_startup_data%': 1,
         }, {
           'v8_use_external_startup_data%': 0,
@@ -1176,7 +1171,6 @@
     'use_system_libjpeg%': '<(use_system_libjpeg)',
     'android_channel%': '<(android_channel)',
     'android_webview_build%': '<(android_webview_build)',
-    'android_webview_telemetry_build%': '<(android_webview_telemetry_build)',
     'icu_use_data_file_flag%': '<(icu_use_data_file_flag)',
     'gyp_managed_install%': 0,
     'create_standalone_apk%': 1,
diff --git a/chrome/browser/DEPS b/chrome/browser/DEPS
index 923e246..e4ed6c7 100644
--- a/chrome/browser/DEPS
+++ b/chrome/browser/DEPS
@@ -98,6 +98,7 @@ include_rules = [
   "+extensions/components/javascript_dialog_extensions_client",
   "+extensions/grit",
   "+extensions/test",
+  "+gin/public/isolate_holder.h",
   "+google/cacheinvalidation",  # Sync invalidation API protobuf files.
   "+google_apis",
   "+google_update",
diff --git a/chrome/browser/chrome_content_browser_client.cc b/chrome/browser/chrome_content_browser_client.cc
index cfab998..25e4fbc 100644
--- a/chrome/browser/chrome_content_browser_client.cc
+++ b/chrome/browser/chrome_content_browser_client.cc
@@ -11,6 +11,7 @@
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/files/scoped_file.h"
+#include "base/i18n/icu_util.h"
 #include "base/lazy_instance.h"
 #include "base/path_service.h"
 #include "base/prefs/pref_service.h"
@@ -122,6 +123,7 @@
 #include "content/public/common/content_descriptors.h"
 #include "content/public/common/url_utils.h"
 #include "content/public/common/web_preferences.h"
+#include "gin/public/isolate_holder.h"
 #include "net/base/mime_util.h"
 #include "net/cookies/canonical_cookie.h"
 #include "net/cookies/cookie_options.h"
@@ -2482,7 +2484,7 @@ void ChromeContentBrowserClient::GetAdditionalMappedFilesForChildProcess(
 
   flags = base::File::FLAG_OPEN | base::File::FLAG_READ;
   base::FilePath icudata_path =
-      app_data_path.AppendASCII("icudtl.dat");
+      app_data_path.AppendASCII(base::i18n::kIcuDataFileName);
   base::File icudata_file(icudata_path, flags);
   DCHECK(icudata_file.IsValid());
   mappings->Transfer(kAndroidICUDataDescriptor,
@@ -2495,9 +2497,9 @@ void ChromeContentBrowserClient::GetAdditionalMappedFilesForChildProcess(
 
   int file_flags = base::File::FLAG_OPEN | base::File::FLAG_READ;
   base::FilePath v8_natives_data_path =
-      v8_data_path.AppendASCII("natives_blob.bin");
+      v8_data_path.AppendASCII(gin::IsolateHolder::kNativesFileName);
   base::FilePath v8_snapshot_data_path =
-      v8_data_path.AppendASCII("snapshot_blob.bin");
+      v8_data_path.AppendASCII(gin::IsolateHolder::kSnapshotFileName);
   base::File v8_natives_data_file(v8_natives_data_path, file_flags);
   base::File v8_snapshot_data_file(v8_snapshot_data_path, file_flags);
   DCHECK(v8_natives_data_file.IsValid());
diff --git a/content/app/DEPS b/content/app/DEPS
index f8429fc..61f7537 100644
--- a/content/app/DEPS
+++ b/content/app/DEPS
@@ -4,5 +4,6 @@ include_rules = [
   "+device/vibration",
   # For loading V8's initial snapshot from external files.
   "+gin/public/isolate_holder.h",
+  "+gin/public/snapshot_fd_data.h",
   "+media/base",  # For initializing media library.
 ]
diff --git a/content/app/content_main_runner.cc b/content/app/content_main_runner.cc
index 2da7dc1..8795067 100644
--- a/content/app/content_main_runner.cc
+++ b/content/app/content_main_runner.cc
@@ -716,10 +716,14 @@ class ContentMainRunnerImpl : public ContentMainRunner {
 #if defined(OS_ANDROID)
     int icudata_fd = base::GlobalDescriptors::GetInstance()->MaybeGet(
         kAndroidICUDataDescriptor);
-    if (icudata_fd != -1)
-      CHECK(base::i18n::InitializeICUWithFileDescriptor(icudata_fd));
-    else
+    if (icudata_fd != -1) {
+      auto icudata_region = base::GlobalDescriptors::GetInstance()->GetRegion(
+          kAndroidICUDataDescriptor);
+      CHECK(base::i18n::InitializeICUWithFileDescriptor(icudata_fd,
+                                                        icudata_region));
+    } else {
       CHECK(base::i18n::InitializeICU());
+    }
 
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
     int v8_natives_fd = base::GlobalDescriptors::GetInstance()->MaybeGet(
@@ -727,8 +731,15 @@ class ContentMainRunnerImpl : public ContentMainRunner {
     int v8_snapshot_fd = base::GlobalDescriptors::GetInstance()->MaybeGet(
         kV8SnapshotDataDescriptor);
     if (v8_natives_fd != -1 && v8_snapshot_fd != -1) {
-      CHECK(gin::IsolateHolder::LoadV8SnapshotFD(v8_natives_fd,
-                                                 v8_snapshot_fd));
+      auto v8_natives_region =
+          base::GlobalDescriptors::GetInstance()->GetRegion(
+              kV8NativesDataDescriptor);
+      auto v8_snapshot_region =
+          base::GlobalDescriptors::GetInstance()->GetRegion(
+              kV8SnapshotDataDescriptor);
+      CHECK(gin::IsolateHolder::LoadV8SnapshotFd(
+          v8_natives_fd, v8_natives_region.offset, v8_natives_region.size,
+          v8_snapshot_fd, v8_snapshot_region.offset, v8_snapshot_region.size));
     } else {
       CHECK(gin::IsolateHolder::LoadV8Snapshot());
     }
diff --git a/content/zygote/zygote_linux.cc b/content/zygote/zygote_linux.cc
index e9b940e..051f791 100644
--- a/content/zygote/zygote_linux.cc
+++ b/content/zygote/zygote_linux.cc
@@ -51,8 +51,8 @@ void SIGCHLDHandler(int signal) {
 
 int LookUpFd(const base::GlobalDescriptors::Mapping& fd_mapping, uint32_t key) {
   for (size_t index = 0; index < fd_mapping.size(); ++index) {
-    if (fd_mapping[index].first == key)
-      return fd_mapping[index].second;
+    if (fd_mapping[index].key == key)
+      return fd_mapping[index].fd;
   }
   return -1;
 }
@@ -506,10 +506,10 @@ base::ProcessId Zygote::ReadArgsAndFork(PickleIterator iter,
     base::GlobalDescriptors::Key key;
     if (!iter.ReadUInt32(&key))
       return -1;
-    mapping.push_back(std::make_pair(key, fds[i]->get()));
+    mapping.push_back(base::GlobalDescriptors::Descriptor(key, fds[i]->get()));
   }
 
-  mapping.push_back(std::make_pair(
+  mapping.push_back(base::GlobalDescriptors::Descriptor(
       static_cast<uint32_t>(kSandboxIPCChannel), GetSandboxFD()));
 
   // Returns twice, once per process.
diff --git a/gin/isolate_holder.cc b/gin/isolate_holder.cc
index 38215b2..ab18ce4 100644
--- a/gin/isolate_holder.cc
+++ b/gin/isolate_holder.cc
@@ -11,6 +11,7 @@
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "base/rand_util.h"
+#include "base/strings/sys_string_conversions.h"
 #include "base/sys_info.h"
 #include "crypto/sha2.h"
 #include "gin/array_buffer.h"
@@ -42,15 +43,23 @@ base::MemoryMappedFile* g_mapped_natives = NULL;
 base::MemoryMappedFile* g_mapped_snapshot = NULL;
 
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
-bool MapV8Files(base::FilePath* natives_path, base::FilePath* snapshot_path,
-                int natives_fd = -1, int snapshot_fd = -1) {
+bool MapV8Files(base::FilePath* natives_path,
+                base::FilePath* snapshot_path,
+                int natives_fd = -1,
+                int snapshot_fd = -1,
+                base::MemoryMappedFile::Region natives_region =
+                    base::MemoryMappedFile::Region::kWholeFile,
+                base::MemoryMappedFile::Region snapshot_region =
+                    base::MemoryMappedFile::Region::kWholeFile) {
   int flags = base::File::FLAG_OPEN | base::File::FLAG_READ;
 
   g_mapped_natives = new base::MemoryMappedFile;
   if (!g_mapped_natives->IsValid()) {
     if (natives_fd == -1
-        ? !g_mapped_natives->Initialize(base::File(*natives_path, flags))
-        : !g_mapped_natives->Initialize(base::File(natives_fd))) {
+            ? !g_mapped_natives->Initialize(base::File(*natives_path, flags),
+                                            natives_region)
+            : !g_mapped_natives->Initialize(base::File(natives_fd),
+                                            natives_region)) {
       delete g_mapped_natives;
       g_mapped_natives = NULL;
       LOG(FATAL) << "Couldn't mmap v8 natives data file";
@@ -61,8 +70,10 @@ bool MapV8Files(base::FilePath* natives_path, base::FilePath* snapshot_path,
   g_mapped_snapshot = new base::MemoryMappedFile;
   if (!g_mapped_snapshot->IsValid()) {
     if (snapshot_fd == -1
-        ? !g_mapped_snapshot->Initialize(base::File(*snapshot_path, flags))
-        : !g_mapped_snapshot->Initialize(base::File(snapshot_fd))) {
+            ? !g_mapped_snapshot->Initialize(base::File(*snapshot_path, flags),
+                                             snapshot_region)
+            : !g_mapped_snapshot->Initialize(base::File(snapshot_fd),
+                                             snapshot_region)) {
       delete g_mapped_snapshot;
       g_mapped_snapshot = NULL;
       LOG(ERROR) << "Couldn't mmap v8 snapshot data file";
@@ -106,6 +117,9 @@ extern const unsigned char g_natives_fingerprint[];
 extern const unsigned char g_snapshot_fingerprint[];
 #endif  // V8_VERIFY_EXTERNAL_STARTUP_DATA
 
+const char IsolateHolder::kNativesFileName[] = "natives_blob.bin";
+const char IsolateHolder::kSnapshotFileName[] = "snapshot_blob.bin";
+
 // static
 bool IsolateHolder::LoadV8Snapshot() {
   if (g_mapped_natives && g_mapped_snapshot)
@@ -116,13 +130,17 @@ bool IsolateHolder::LoadV8Snapshot() {
   PathService::Get(v8_snapshot_dir, &data_path);
   DCHECK(!data_path.empty());
 
-  base::FilePath natives_path = data_path.AppendASCII("natives_blob.bin");
-  base::FilePath snapshot_path = data_path.AppendASCII("snapshot_blob.bin");
+  base::FilePath natives_path = data_path.AppendASCII(kNativesFileName);
+  base::FilePath snapshot_path = data_path.AppendASCII(kSnapshotFileName);
 #else  // !defined(OS_MACOSX)
+  base::ScopedCFTypeRef<CFStringRef> natives_file_name(
+      base::SysUTF8ToCFStringRef(kNativesFileName));
   base::FilePath natives_path = base::mac::PathForFrameworkBundleResource(
-      CFSTR("natives_blob.bin"));
+      natives_file_name);
+  base::ScopedCFTypeRef<CFStringRef> snapshot_file_name(
+      base::SysUTF8ToCFStringRef(kSnapshotFileName));
   base::FilePath snapshot_path = base::mac::PathForFrameworkBundleResource(
-      CFSTR("snapshot_blob.bin"));
+      snapshot_file_name);
   DCHECK(!natives_path.empty());
   DCHECK(!snapshot_path.empty());
 #endif  // !defined(OS_MACOSX)
@@ -139,11 +157,31 @@ bool IsolateHolder::LoadV8Snapshot() {
 }
 
 //static
-bool IsolateHolder::LoadV8SnapshotFD(int natives_fd, int snapshot_fd) {
+bool IsolateHolder::LoadV8SnapshotFd(int natives_fd,
+                               int64 natives_offset,
+                               int64 natives_size,
+                               int snapshot_fd,
+                               int64 snapshot_offset,
+                               int64 snapshot_size) {
   if (g_mapped_natives && g_mapped_snapshot)
     return true;
 
-  return MapV8Files(NULL, NULL, natives_fd, snapshot_fd);
+  base::MemoryMappedFile::Region natives_region =
+      base::MemoryMappedFile::Region::kWholeFile;
+  if (natives_size != 0 || natives_offset != 0) {
+    natives_region =
+        base::MemoryMappedFile::Region(natives_offset, natives_size);
+  }
+
+  base::MemoryMappedFile::Region snapshot_region =
+      base::MemoryMappedFile::Region::kWholeFile;
+  if (natives_size != 0 || natives_offset != 0) {
+    snapshot_region =
+        base::MemoryMappedFile::Region(snapshot_offset, snapshot_size);
+  }
+
+  return MapV8Files(
+      NULL, NULL, natives_fd, snapshot_fd, natives_region, snapshot_region);
 }
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
 
diff --git a/gin/public/isolate_holder.h b/gin/public/isolate_holder.h
index 64fc952..44d1d89 100644
--- a/gin/public/isolate_holder.h
+++ b/gin/public/isolate_holder.h
@@ -33,7 +33,7 @@ class GIN_EXPORT IsolateHolder {
   // Should be invoked once before creating IsolateHolder instances to
   // initialize V8 and Gin. In case V8_USE_EXTERNAL_STARTUP_DATA is defined,
   // V8's initial snapshot should be loaded (by calling LoadV8Snapshot or
-  // LoadV8SnapshotFD) before calling Initialize.
+  // LoadV8SnapshotFd) before calling Initialize.
   static void Initialize(ScriptMode mode,
                          v8::ArrayBuffer::Allocator* allocator);
 
@@ -52,7 +52,15 @@ class GIN_EXPORT IsolateHolder {
   void RemoveRunMicrotasksObserver();
 
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
-  static bool LoadV8SnapshotFD(int natives_fd, int snapshot_fd);
+  static const char kNativesFileName[];
+  static const char kSnapshotFileName[];
+
+  static bool LoadV8SnapshotFd(int natives_fd,
+                               int64 natives_offset,
+                               int64 natives_size,
+                               int snapshot_fd,
+                               int64 snapshot_offset,
+                               int64 snapshot_size);
   static bool LoadV8Snapshot();
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
   static void GetV8ExternalSnapshotData(const char** natives_data_out,