Move V8 snapshot loading code from isolate_holder to gin/v8_startup_data.{h,cc}.

isolate_holder.h is public and used by blink and therefore cannot refer to types from base. As part of porting this to other platforms we needed to load snapshots from BaseFile descriptors.

BUG=421063

Review URL: https://codereview.chromium.org/1011133006

Cr-Commit-Position: refs/heads/master@{#323886}

26 files changed, 350 insertions, 277 deletions

diff --git a/chrome/browser/DEPS b/chrome/browser/DEPS
index 7c78fa9..0368828 100644
--- a/chrome/browser/DEPS
+++ b/chrome/browser/DEPS
@@ -106,7 +106,7 @@ include_rules = [
   "+extensions/components/javascript_dialog_extensions_client",
   "+extensions/grit",
   "+extensions/test",
-  "+gin/public/isolate_holder.h",
+  "+gin",
   "+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 c644b41..51ab5ea 100644
--- a/chrome/browser/chrome_content_browser_client.cc
+++ b/chrome/browser/chrome_content_browser_client.cc
@@ -117,7 +117,7 @@
 #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 "gin/v8_initializer.h"
 #include "net/base/mime_util.h"
 #include "net/cookies/canonical_cookie.h"
 #include "net/cookies/cookie_options.h"
@@ -2185,14 +2185,14 @@ void ChromeContentBrowserClient::GetAdditionalMappedFilesForChildProcess(
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
   if (v8_snapshot_fd_.get() == -1 && v8_natives_fd_.get() == -1) {
     base::FilePath v8_data_path;
-    PathService::Get(gin::IsolateHolder::kV8SnapshotBasePathKey, &v8_data_path);
+    PathService::Get(gin::V8Initializer::kV8SnapshotBasePathKey, &v8_data_path);
     DCHECK(!v8_data_path.empty());
 
     int file_flags = base::File::FLAG_OPEN | base::File::FLAG_READ;
     base::FilePath v8_natives_data_path =
-        v8_data_path.AppendASCII(gin::IsolateHolder::kNativesFileName);
+        v8_data_path.AppendASCII(gin::V8Initializer::kNativesFileName);
     base::FilePath v8_snapshot_data_path =
-        v8_data_path.AppendASCII(gin::IsolateHolder::kSnapshotFileName);
+        v8_data_path.AppendASCII(gin::V8Initializer::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/chrome/plugin/DEPS b/chrome/plugin/DEPS
index eca72a4..8c270f4 100644
--- a/chrome/plugin/DEPS
+++ b/chrome/plugin/DEPS
@@ -1,5 +1,6 @@
 include_rules = [
   "+content/public/plugin",
   "+gin/public/isolate_holder.h",
+  "+gin/v8_initializer.h",
   "+media/base",
 ]
diff --git a/chrome/plugin/chrome_content_plugin_client.cc b/chrome/plugin/chrome_content_plugin_client.cc
index 87c20d0..fd4c013 100644
--- a/chrome/plugin/chrome_content_plugin_client.cc
+++ b/chrome/plugin/chrome_content_plugin_client.cc
@@ -18,14 +18,14 @@
 #endif
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
-#include "gin/public/isolate_holder.h"
+#include "gin/v8_initializer.h"
 #endif
 
 namespace chrome {
 
 void ChromeContentPluginClient::PreSandboxInitialization() {
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
-  gin::IsolateHolder::LoadV8Snapshot();
+  gin::V8Initializer::LoadV8Snapshot();
 #endif
 
 #if defined(ENABLE_REMOTING)
diff --git a/components/pdf/renderer/ppb_pdf_impl.cc b/components/pdf/renderer/ppb_pdf_impl.cc
index 6349543..3553c47 100644
--- a/components/pdf/renderer/ppb_pdf_impl.cc
+++ b/components/pdf/renderer/ppb_pdf_impl.cc
@@ -18,7 +18,7 @@
 #include "content/public/renderer/pepper_plugin_instance.h"
 #include "content/public/renderer/render_thread.h"
 #include "content/public/renderer/render_view.h"
-#include "gin/public/isolate_holder.h"
+#include "gin/v8_initializer.h"
 #include "ppapi/c/pp_resource.h"
 #include "ppapi/c/private/ppb_pdf.h"
 #include "ppapi/c/trusted/ppb_browser_font_trusted.h"
@@ -343,8 +343,8 @@ void GetV8ExternalSnapshotData(PP_Instance instance_id,
                                int* natives_size_out,
                                const char** snapshot_data_out,
                                int* snapshot_size_out) {
-  gin::IsolateHolder::GetV8ExternalSnapshotData(natives_data_out,
-      natives_size_out, snapshot_data_out, snapshot_size_out);
+  gin::V8Initializer::GetV8ExternalSnapshotData(
+      natives_data_out, natives_size_out, snapshot_data_out, snapshot_size_out);
 }
 
 const PPB_PDF ppb_pdf = {                      //
diff --git a/content/app/DEPS b/content/app/DEPS
index 61f7537..b6d8307 100644
--- a/content/app/DEPS
+++ b/content/app/DEPS
@@ -5,5 +5,6 @@ include_rules = [
   # For loading V8's initial snapshot from external files.
   "+gin/public/isolate_holder.h",
   "+gin/public/snapshot_fd_data.h",
+  "+gin/v8_initializer.h",
   "+media/base",  # For initializing media library.
 ]
diff --git a/content/app/content_main_runner.cc b/content/app/content_main_runner.cc
index 7c8e7eb..f14c6eb 100644
--- a/content/app/content_main_runner.cc
+++ b/content/app/content_main_runner.cc
@@ -51,7 +51,7 @@
 #include "ui/base/ui_base_switches.h"
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
-#include "gin/public/isolate_holder.h"
+#include "gin/v8_initializer.h"
 #endif
 
 #if defined(USE_TCMALLOC)
@@ -718,14 +718,14 @@ class ContentMainRunnerImpl : public ContentMainRunner {
     if (v8_natives_fd != -1 && v8_snapshot_fd != -1) {
       auto v8_natives_region = g_fds->GetRegion(kV8NativesDataDescriptor);
       auto v8_snapshot_region = g_fds->GetRegion(kV8SnapshotDataDescriptor);
-      CHECK(gin::IsolateHolder::LoadV8SnapshotFd(
+      CHECK(gin::V8Initializer::LoadV8SnapshotFromFD(
           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());
+      CHECK(gin::V8Initializer::LoadV8Snapshot());
     }
 #else
-    CHECK(gin::IsolateHolder::LoadV8Snapshot());
+    CHECK(gin::V8Initializer::LoadV8Snapshot());
 #endif  // OS_POSIX && !OS_MACOSX
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
 
diff --git a/content/public/test/DEPS b/content/public/test/DEPS
index 43a7d3c..e897ad3 100644
--- a/content/public/test/DEPS
+++ b/content/public/test/DEPS
@@ -9,7 +9,7 @@ specific_include_rules = {
   ".*\.cc": [
     # Testing utilities can access anything in content/
     "+content",
-    "+gin/public/isolate_holder.h",
+    "+gin/v8_initializer.h",
     "+media/base",
     "+third_party/iaccessible2",
     "+ui/base/resource/resource_bundle.h",
diff --git a/content/public/test/content_test_suite_base.cc b/content/public/test/content_test_suite_base.cc
index 81821b0..a19b03f 100644
--- a/content/public/test/content_test_suite_base.cc
+++ b/content/public/test/content_test_suite_base.cc
@@ -44,7 +44,7 @@
 #endif
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
-#include "gin/public/isolate_holder.h"
+#include "gin/v8_initializer.h"
 #endif
 
 namespace content {
@@ -73,7 +73,7 @@ void ContentTestSuiteBase::Initialize() {
   base::StatisticsRecorder::Initialize();
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
-  gin::IsolateHolder::LoadV8Snapshot();
+  gin::V8Initializer::LoadV8Snapshot();
 #endif
 
 #if defined(OS_ANDROID)
diff --git a/content/shell/DEPS b/content/shell/DEPS
index a46f5cf..3dfeb6b 100644
--- a/content/shell/DEPS
+++ b/content/shell/DEPS
@@ -1,5 +1,6 @@
 include_rules = [
   "+gin/public",
+  "+gin/v8_initializer.h",
   "+v8/include",
 
   # For chromeos build config
diff --git a/content/shell/browser/shell_content_browser_client.cc b/content/shell/browser/shell_content_browser_client.cc
index c10761f..9cf8473 100644
--- a/content/shell/browser/shell_content_browser_client.cc
+++ b/content/shell/browser/shell_content_browser_client.cc
@@ -34,7 +34,7 @@
 #include "content/shell/common/shell_messages.h"
 #include "content/shell/common/shell_switches.h"
 #include "content/shell/common/webkit_test_helpers.h"
-#include "gin/public/isolate_holder.h"
+#include "gin/v8_initializer.h"
 #include "net/url_request/url_request_context_getter.h"
 #include "url/gurl.h"
 
@@ -335,14 +335,14 @@ void ShellContentBrowserClient::GetAdditionalMappedFilesForChildProcess(
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
   if (v8_snapshot_fd_.get() == -1 && v8_natives_fd_.get() == -1) {
     base::FilePath v8_data_path;
-    PathService::Get(gin::IsolateHolder::kV8SnapshotBasePathKey, &v8_data_path);
+    PathService::Get(gin::V8Initializer::kV8SnapshotBasePathKey, &v8_data_path);
     DCHECK(!v8_data_path.empty());
 
     int file_flags = base::File::FLAG_OPEN | base::File::FLAG_READ;
     base::FilePath v8_natives_data_path =
-        v8_data_path.AppendASCII(gin::IsolateHolder::kNativesFileName);
+        v8_data_path.AppendASCII(gin::V8Initializer::kNativesFileName);
     base::FilePath v8_snapshot_data_path =
-        v8_data_path.AppendASCII(gin::IsolateHolder::kSnapshotFileName);
+        v8_data_path.AppendASCII(gin::V8Initializer::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/test/DEPS b/content/test/DEPS
index 7d1b3d9..b0b89c0 100644
--- a/content/test/DEPS
+++ b/content/test/DEPS
@@ -4,7 +4,7 @@ include_rules = [
   # Testing utilities can access anything in content/
   "+content",
   # For loading V8's initial snapshot from external files.
-  "+gin/public/isolate_holder.h",
+  "+gin/v8_initializer.h",
   "+media/audio", # For AudioParameters in WebRTC tests.
   "+media/base",  # For ChannelLayout in WebRTC tests.
   "+ui/base/resource/data_pack.h",
diff --git a/content/test/content_test_launcher.cc b/content/test/content_test_launcher.cc
index 7c7eb27..9b30fdb 100644
--- a/content/test/content_test_launcher.cc
+++ b/content/test/content_test_launcher.cc
@@ -21,7 +21,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
-#include "gin/public/isolate_holder.h"
+#include "gin/v8_initializer.h"
 #endif
 
 #if defined(OS_ANDROID)
@@ -57,7 +57,7 @@ class ContentBrowserTestSuite : public ContentTestSuiteBase {
     base::i18n::InitializeICU();
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
-    gin::IsolateHolder::LoadV8Snapshot();
+    gin::V8Initializer::LoadV8Snapshot();
 #endif
 
     // This needs to be done before base::TestSuite::Initialize() is called,
diff --git a/content/test/test_blink_web_unit_test_support.cc b/content/test/test_blink_web_unit_test_support.cc
index 9010d0d..1326e7d 100644
--- a/content/test/test_blink_web_unit_test_support.cc
+++ b/content/test/test_blink_web_unit_test_support.cc
@@ -39,7 +39,7 @@
 #endif
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
-#include "gin/public/isolate_holder.h"
+#include "gin/v8_initializer.h"
 #endif
 
 namespace content {
@@ -53,7 +53,7 @@ TestBlinkWebUnitTestSupport::TestBlinkWebUnitTestSupport() {
   mock_clipboard_.reset(new MockWebClipboardImpl());
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
-  gin::IsolateHolder::LoadV8Snapshot();
+  gin::V8Initializer::LoadV8Snapshot();
 #endif
 
   if (base::MessageLoopProxy::current()) {
diff --git a/gin/BUILD.gn b/gin/BUILD.gn
index 5446d56..9fe5a12 100644
--- a/gin/BUILD.gn
+++ b/gin/BUILD.gn
@@ -56,6 +56,8 @@ component("gin") {
     "shell_runner.h",
     "try_catch.cc",
     "try_catch.h",
+    "v8_initializer.cc",
+    "v8_initializer.h",
     "v8_platform.cc",
     "wrappable.cc",
     "wrappable.h",
diff --git a/gin/gin.gyp b/gin/gin.gyp
index 096c120..46afc97 100644
--- a/gin/gin.gyp
+++ b/gin/gin.gyp
@@ -73,6 +73,8 @@
         'shell_runner.h',
         'try_catch.cc',
         'try_catch.h',
+        'v8_initializer.h',
+        'v8_initializer.cc',
         'v8_platform.cc',
         'wrappable.cc',
         'wrappable.h',
diff --git a/gin/isolate_holder.cc b/gin/isolate_holder.cc
index 317b582..3cc3238 100644
--- a/gin/isolate_holder.cc
+++ b/gin/isolate_holder.cc
@@ -7,214 +7,24 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "base/files/memory_mapped_file.h"
 #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"
 #include "gin/debug_impl.h"
 #include "gin/function_template.h"
 #include "gin/per_isolate_data.h"
-#include "gin/public/v8_platform.h"
 #include "gin/run_microtasks_observer.h"
-
-#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
-#if defined(OS_MACOSX)
-#include "base/mac/foundation_util.h"
-#endif  // OS_MACOSX
-#include "base/path_service.h"
-#endif  // V8_USE_EXTERNAL_STARTUP_DATA
+#include "gin/v8_initializer.h"
 
 namespace gin {
 
 namespace {
-
-v8::ArrayBuffer::Allocator* g_array_buffer_allocator = NULL;
-
-bool GenerateEntropy(unsigned char* buffer, size_t amount) {
-  base::RandBytes(buffer, amount);
-  return true;
-}
-
-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,
-                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 !defined(OS_WIN)
-    if (natives_fd == -1
-            ? !g_mapped_natives->Initialize(base::File(*natives_path, flags),
-                                            natives_region)
-            : !g_mapped_natives->Initialize(base::File(natives_fd),
-                                            natives_region)) {
-#else
-    if (!g_mapped_natives->Initialize(base::File(*natives_path, flags),
-                                      natives_region)) {
-#endif  // !OS_WIN
-      delete g_mapped_natives;
-      g_mapped_natives = NULL;
-      LOG(FATAL) << "Couldn't mmap v8 natives data file";
-      return false;
-    }
-  }
-
-  g_mapped_snapshot = new base::MemoryMappedFile;
-  if (!g_mapped_snapshot->IsValid()) {
-#if !defined(OS_WIN)
-    if (snapshot_fd == -1
-            ? !g_mapped_snapshot->Initialize(base::File(*snapshot_path, flags),
-                                             snapshot_region)
-            : !g_mapped_snapshot->Initialize(base::File(snapshot_fd),
-                                             snapshot_region)) {
-#else
-    if (!g_mapped_snapshot->Initialize(base::File(*snapshot_path, flags),
-                                       snapshot_region)) {
-#endif  // !OS_WIN
-      delete g_mapped_snapshot;
-      g_mapped_snapshot = NULL;
-      LOG(ERROR) << "Couldn't mmap v8 snapshot data file";
-      return false;
-    }
-  }
-
-  return true;
-}
-
-#if defined(V8_VERIFY_EXTERNAL_STARTUP_DATA)
-bool VerifyV8SnapshotFile(base::MemoryMappedFile* snapshot_file,
-                          const unsigned char* fingerprint) {
-  unsigned char output[crypto::kSHA256Length];
-  crypto::SHA256HashString(
-      base::StringPiece(reinterpret_cast<const char*>(snapshot_file->data()),
-                        snapshot_file->length()),
-      output, sizeof(output));
-  return !memcmp(fingerprint, output, sizeof(output));
-}
-#endif  // V8_VERIFY_EXTERNAL_STARTUP_DATA
-#endif  // V8_USE_EXTERNAL_STARTUP_DATA
-
+v8::ArrayBuffer::Allocator* g_array_buffer_allocator = nullptr;
 }  // namespace
 
-#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
-
-#if defined(V8_VERIFY_EXTERNAL_STARTUP_DATA)
-// Defined in gen/gin/v8_snapshot_fingerprint.cc
-extern const unsigned char g_natives_fingerprint[];
-extern const unsigned char g_snapshot_fingerprint[];
-#endif  // V8_VERIFY_EXTERNAL_STARTUP_DATA
-
-#if !defined(OS_MACOSX)
-const int IsolateHolder::kV8SnapshotBasePathKey =
-#if defined(OS_ANDROID)
-    base::DIR_ANDROID_APP_DATA;
-#elif defined(OS_POSIX)
-    base::DIR_EXE;
-#elif defined(OS_WIN)
-    base::DIR_MODULE;
-#endif  // OS_ANDROID
-#endif  // !OS_MACOSX
-
-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)
-    return true;
-
-#if !defined(OS_MACOSX)
-  base::FilePath data_path;
-  PathService::Get(kV8SnapshotBasePathKey, &data_path);
-  DCHECK(!data_path.empty());
-
-  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(
-      natives_file_name);
-  base::ScopedCFTypeRef<CFStringRef> snapshot_file_name(
-      base::SysUTF8ToCFStringRef(kSnapshotFileName));
-  base::FilePath snapshot_path = base::mac::PathForFrameworkBundleResource(
-      snapshot_file_name);
-  DCHECK(!natives_path.empty());
-  DCHECK(!snapshot_path.empty());
-#endif  // !defined(OS_MACOSX)
-
-  if (!MapV8Files(&natives_path, &snapshot_path))
-    return false;
-
-#if defined(V8_VERIFY_EXTERNAL_STARTUP_DATA)
-  return VerifyV8SnapshotFile(g_mapped_natives, g_natives_fingerprint) &&
-         VerifyV8SnapshotFile(g_mapped_snapshot, g_snapshot_fingerprint);
-#else
-  return true;
-#endif  // V8_VERIFY_EXTERNAL_STARTUP_DATA
-}
-
-//static
-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;
-
-  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
-
-//static
-void IsolateHolder::GetV8ExternalSnapshotData(const char** natives_data_out,
-                                              int* natives_size_out,
-                                              const char** snapshot_data_out,
-                                              int* snapshot_size_out) {
-  if (!g_mapped_natives || !g_mapped_snapshot) {
-    *natives_data_out = *snapshot_data_out = NULL;
-    *natives_size_out = *snapshot_size_out = 0;
-    return;
-  }
-  *natives_data_out = reinterpret_cast<const char*>(g_mapped_natives->data());
-  *snapshot_data_out = reinterpret_cast<const char*>(g_mapped_snapshot->data());
-  *natives_size_out = static_cast<int>(g_mapped_natives->length());
-  *snapshot_size_out = static_cast<int>(g_mapped_snapshot->length());
-}
-
 IsolateHolder::IsolateHolder() {
-  CHECK(g_array_buffer_allocator)
-      << "You need to invoke gin::IsolateHolder::Initialize first";
+  v8::ArrayBuffer::Allocator* allocator = g_array_buffer_allocator;
+  CHECK(allocator) << "You need to invoke gin::IsolateHolder::Initialize first";
   v8::Isolate::CreateParams params;
   params.entry_hook = DebugImpl::GetFunctionEntryHook();
   params.code_event_handler = DebugImpl::GetJitCodeEventHandler();
@@ -222,7 +32,7 @@ IsolateHolder::IsolateHolder() {
                                        base::SysInfo::AmountOfVirtualMemory(),
                                        base::SysInfo::NumberOfProcessors());
   isolate_ = v8::Isolate::New(params);
-  isolate_data_.reset(new PerIsolateData(isolate_, g_array_buffer_allocator));
+  isolate_data_.reset(new PerIsolateData(isolate_, allocator));
 #if defined(OS_WIN)
   {
     void* code_range;
@@ -259,30 +69,8 @@ IsolateHolder::~IsolateHolder() {
 void IsolateHolder::Initialize(ScriptMode mode,
                                v8::ArrayBuffer::Allocator* allocator) {
   CHECK(allocator);
-  static bool v8_is_initialized = false;
-  if (v8_is_initialized)
-    return;
-  v8::V8::InitializePlatform(V8Platform::Get());
-  v8::V8::SetArrayBufferAllocator(allocator);
+  gin::V8Initializer::Initialize(mode, allocator);
   g_array_buffer_allocator = allocator;
-  if (mode == gin::IsolateHolder::kStrictMode) {
-    static const char use_strict[] = "--use_strict";
-    v8::V8::SetFlagsFromString(use_strict, sizeof(use_strict) - 1);
-  }
-  v8::V8::SetEntropySource(&GenerateEntropy);
-#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
-  v8::StartupData natives;
-  natives.data = reinterpret_cast<const char*>(g_mapped_natives->data());
-  natives.raw_size = static_cast<int>(g_mapped_natives->length());
-  v8::V8::SetNativesDataBlob(&natives);
-
-  v8::StartupData snapshot;
-  snapshot.data = reinterpret_cast<const char*>(g_mapped_snapshot->data());
-  snapshot.raw_size = static_cast<int>(g_mapped_snapshot->length());
-  v8::V8::SetSnapshotDataBlob(&snapshot);
-#endif  // V8_USE_EXTERNAL_STARTUP_DATA
-  v8::V8::Initialize();
-  v8_is_initialized = true;
 }
 
 void IsolateHolder::AddRunMicrotasksObserver() {
@@ -297,4 +85,13 @@ void IsolateHolder::RemoveRunMicrotasksObserver() {
   task_observer_.reset();
 }
 
+#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+
+// static
+bool IsolateHolder::LoadV8Snapshot() {
+  return V8Initializer::LoadV8Snapshot();
+}
+
+#endif  // V8_USE_EXTERNAL_STARTUP_DATA
+
 }  // namespace gin
diff --git a/gin/public/isolate_holder.h b/gin/public/isolate_holder.h
index 7968b1df..d2275ed 100644
--- a/gin/public/isolate_holder.h
+++ b/gin/public/isolate_holder.h
@@ -31,9 +31,10 @@ class GIN_EXPORT IsolateHolder {
   ~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.
+  // initialize V8 and Gin. In case V8_USE_EXTERNAL_STARTUP_DATA is
+  // defined, V8's initial snapshot should be loaded (by calling
+  // V8Initializer::LoadV8SnapshotFromFD or
+  // V8Initializer::LoadV8Snapshot) before calling this method.
   static void Initialize(ScriptMode mode,
                          v8::ArrayBuffer::Allocator* allocator);
 
@@ -52,22 +53,13 @@ class GIN_EXPORT IsolateHolder {
   void RemoveRunMicrotasksObserver();
 
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
-  static const int kV8SnapshotBasePathKey;
-  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);
+
+  // Deprecated and to be removed: Use gin::V8Initializer::LoadV8Snapshot()
+  // Load V8 snapshot from default resources. Returns true on success or
+  // snapshot is already loaded, false otherwise.
   static bool LoadV8Snapshot();
+
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
-  static void GetV8ExternalSnapshotData(const char** natives_data_out,
-                                        int* natives_size_out,
-                                        const char** snapshot_data_out,
-                                        int* snapshot_size_out);
 
  private:
   v8::Isolate* isolate_;
diff --git a/gin/shell/gin_main.cc b/gin/shell/gin_main.cc
index 532f996..d3bab72 100644
--- a/gin/shell/gin_main.cc
+++ b/gin/shell/gin_main.cc
@@ -13,6 +13,7 @@
 #include "gin/modules/module_runner_delegate.h"
 #include "gin/public/isolate_holder.h"
 #include "gin/try_catch.h"
+#include "gin/v8_initializer.h"
 
 namespace gin {
 namespace {
@@ -60,7 +61,7 @@ int main(int argc, char** argv) {
   base::CommandLine::Init(argc, argv);
   base::i18n::InitializeICU();
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
-  gin::IsolateHolder::LoadV8Snapshot();
+  gin::V8Initializer::LoadV8Snapshot();
 #endif
 
   gin::IsolateHolder::Initialize(gin::IsolateHolder::kStrictMode,
diff --git a/gin/shell_runner_unittest.cc b/gin/shell_runner_unittest.cc
index 7134de1..340b673 100644
--- a/gin/shell_runner_unittest.cc
+++ b/gin/shell_runner_unittest.cc
@@ -8,6 +8,7 @@
 #include "gin/array_buffer.h"
 #include "gin/converter.h"
 #include "gin/public/isolate_holder.h"
+#include "gin/v8_initializer.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
@@ -25,7 +26,7 @@ TEST(RunnerTest, Run) {
   std::string source = "this.result = 'PASS';\n";
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
-  gin::IsolateHolder::LoadV8Snapshot();
+  gin::V8Initializer::LoadV8Snapshot();
 #endif
 
   gin::IsolateHolder::Initialize(gin::IsolateHolder::kStrictMode,
diff --git a/gin/test/file_runner.cc b/gin/test/file_runner.cc
index b639d06..723ab98 100644
--- a/gin/test/file_runner.cc
+++ b/gin/test/file_runner.cc
@@ -17,12 +17,9 @@
 #include "gin/test/gc.h"
 #include "gin/test/gtest.h"
 #include "gin/try_catch.h"
+#include "gin/v8_initializer.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
-#ifdef V8_USE_EXTERNAL_STARTUP_DATA
-#include "gin/public/isolate_holder.h"
-#endif
-
 namespace gin {
 
 namespace {
@@ -63,11 +60,12 @@ void RunTestFromFile(const base::FilePath& path, FileRunnerDelegate* delegate,
   base::MessageLoop message_loop;
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
-  gin::IsolateHolder::LoadV8Snapshot();
+  gin::V8Initializer::LoadV8Snapshot();
 #endif
 
   gin::IsolateHolder::Initialize(gin::IsolateHolder::kStrictMode,
                                  gin::ArrayBufferAllocator::SharedInstance());
+
   gin::IsolateHolder instance;
   gin::ShellRunner runner(delegate, instance.isolate());
   {
diff --git a/gin/test/v8_test.cc b/gin/test/v8_test.cc
index a022511..aad291d 100644
--- a/gin/test/v8_test.cc
+++ b/gin/test/v8_test.cc
@@ -6,10 +6,7 @@
 
 #include "gin/array_buffer.h"
 #include "gin/public/isolate_holder.h"
-
-#ifdef V8_USE_EXTERNAL_STARTUP_DATA
-#include "gin/public/isolate_holder.h"
-#endif
+#include "gin/v8_initializer.h"
 
 using v8::Context;
 using v8::Local;
@@ -25,10 +22,11 @@ V8Test::~V8Test() {
 
 void V8Test::SetUp() {
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
-  gin::IsolateHolder::LoadV8Snapshot();
+  gin::V8Initializer::LoadV8Snapshot();
 #endif
   gin::IsolateHolder::Initialize(gin::IsolateHolder::kStrictMode,
                                  gin::ArrayBufferAllocator::SharedInstance());
+
   instance_.reset(new gin::IsolateHolder);
   instance_->isolate()->Enter();
   HandleScope handle_scope(instance_->isolate());
diff --git a/gin/v8_initializer.cc b/gin/v8_initializer.cc
new file mode 100644
index 0000000..76f227d
--- /dev/null
+++ b/gin/v8_initializer.cc
@@ -0,0 +1,221 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "gin/v8_initializer.h"
+
+#include "base/basictypes.h"
+#include "base/files/file.h"
+#include "base/files/file_path.h"
+#include "base/files/memory_mapped_file.h"
+#include "base/logging.h"
+#include "base/rand_util.h"
+#include "base/strings/sys_string_conversions.h"
+#include "crypto/sha2.h"
+
+#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+#if defined(OS_MACOSX)
+#include "base/mac/foundation_util.h"
+#endif  // OS_MACOSX
+#include "base/path_service.h"
+#endif  // V8_USE_EXTERNAL_STARTUP_DATA
+
+namespace gin {
+
+namespace {
+
+bool GenerateEntropy(unsigned char* buffer, size_t amount) {
+  base::RandBytes(buffer, amount);
+  return true;
+}
+
+base::MemoryMappedFile* g_mapped_natives = nullptr;
+base::MemoryMappedFile* g_mapped_snapshot = nullptr;
+
+#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+bool MapV8Files(base::File natives_file,
+                base::File snapshot_file,
+                base::MemoryMappedFile::Region natives_region =
+                    base::MemoryMappedFile::Region::kWholeFile,
+                base::MemoryMappedFile::Region snapshot_region =
+                    base::MemoryMappedFile::Region::kWholeFile) {
+  g_mapped_natives = new base::MemoryMappedFile;
+  if (!g_mapped_natives->IsValid()) {
+    if (!g_mapped_natives->Initialize(natives_file.Pass(), natives_region)) {
+      delete g_mapped_natives;
+      g_mapped_natives = NULL;
+      LOG(FATAL) << "Couldn't mmap v8 natives data file";
+      return false;
+    }
+  }
+
+  g_mapped_snapshot = new base::MemoryMappedFile;
+  if (!g_mapped_snapshot->IsValid()) {
+    if (!g_mapped_snapshot->Initialize(snapshot_file.Pass(), snapshot_region)) {
+      delete g_mapped_snapshot;
+      g_mapped_snapshot = NULL;
+      LOG(ERROR) << "Couldn't mmap v8 snapshot data file";
+      return false;
+    }
+  }
+
+  return true;
+}
+
+#if defined(V8_VERIFY_EXTERNAL_STARTUP_DATA)
+bool VerifyV8SnapshotFile(base::MemoryMappedFile* snapshot_file,
+                          const unsigned char* fingerprint) {
+  unsigned char output[crypto::kSHA256Length];
+  crypto::SHA256HashString(
+      base::StringPiece(reinterpret_cast<const char*>(snapshot_file->data()),
+                        snapshot_file->length()),
+      output, sizeof(output));
+  return !memcmp(fingerprint, output, sizeof(output));
+}
+#endif  // V8_VERIFY_EXTERNAL_STARTUP_DATA
+#endif  // V8_USE_EXTERNAL_STARTUP_DATA
+
+}  // namespace
+
+#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+
+#if defined(V8_VERIFY_EXTERNAL_STARTUP_DATA)
+// Defined in gen/gin/v8_snapshot_fingerprint.cc
+extern const unsigned char g_natives_fingerprint[];
+extern const unsigned char g_snapshot_fingerprint[];
+#endif  // V8_VERIFY_EXTERNAL_STARTUP_DATA
+
+#if !defined(OS_MACOSX)
+const int V8Initializer::kV8SnapshotBasePathKey =
+#if defined(OS_ANDROID)
+    base::DIR_ANDROID_APP_DATA;
+#elif defined(OS_POSIX)
+    base::DIR_EXE;
+#elif defined(OS_WIN)
+    base::DIR_MODULE;
+#endif  // OS_ANDROID
+#endif  // !OS_MACOSX
+
+const char V8Initializer::kNativesFileName[] = "natives_blob.bin";
+const char V8Initializer::kSnapshotFileName[] = "snapshot_blob.bin";
+
+// static
+bool V8Initializer::LoadV8Snapshot() {
+  if (g_mapped_natives && g_mapped_snapshot)
+    return true;
+
+#if !defined(OS_MACOSX)
+  base::FilePath data_path;
+  PathService::Get(kV8SnapshotBasePathKey, &data_path);
+  DCHECK(!data_path.empty());
+
+  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(natives_file_name);
+  base::ScopedCFTypeRef<CFStringRef> snapshot_file_name(
+      base::SysUTF8ToCFStringRef(kSnapshotFileName));
+  base::FilePath snapshot_path =
+      base::mac::PathForFrameworkBundleResource(snapshot_file_name);
+  DCHECK(!natives_path.empty());
+  DCHECK(!snapshot_path.empty());
+#endif  // !defined(OS_MACOSX)
+
+  int flags = base::File::FLAG_OPEN | base::File::FLAG_READ;
+  if (!MapV8Files(base::File(natives_path, flags),
+                  base::File(snapshot_path, flags)))
+    return false;
+
+#if defined(V8_VERIFY_EXTERNAL_STARTUP_DATA)
+  return VerifyV8SnapshotFile(g_mapped_natives, g_natives_fingerprint) &&
+         VerifyV8SnapshotFile(g_mapped_snapshot, g_snapshot_fingerprint);
+#else
+  return true;
+#endif  // V8_VERIFY_EXTERNAL_STARTUP_DATA
+}
+
+// static
+bool V8Initializer::LoadV8SnapshotFromFD(base::PlatformFile natives_pf,
+                                         int64 natives_offset,
+                                         int64 natives_size,
+                                         base::PlatformFile snapshot_pf,
+                                         int64 snapshot_offset,
+                                         int64 snapshot_size) {
+  if (g_mapped_natives && g_mapped_snapshot)
+    return true;
+
+  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(base::File(natives_pf), base::File(snapshot_pf),
+                    natives_region, snapshot_region);
+}
+
+#endif  // V8_USE_EXTERNAL_STARTUP_DATA
+
+// static
+void V8Initializer::Initialize(gin::IsolateHolder::ScriptMode mode,
+                               v8::ArrayBuffer::Allocator* allocator) {
+  CHECK(allocator);
+
+  static bool v8_is_initialized = false;
+  if (v8_is_initialized)
+    return;
+
+  v8::V8::InitializePlatform(V8Platform::Get());
+  v8::V8::SetArrayBufferAllocator(allocator);
+
+  if (gin::IsolateHolder::kStrictMode == mode) {
+    static const char use_strict[] = "--use_strict";
+    v8::V8::SetFlagsFromString(use_strict, sizeof(use_strict) - 1);
+  }
+
+#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+  v8::StartupData natives;
+  natives.data = reinterpret_cast<const char*>(g_mapped_natives->data());
+  natives.raw_size = static_cast<int>(g_mapped_natives->length());
+  v8::V8::SetNativesDataBlob(&natives);
+
+  v8::StartupData snapshot;
+  snapshot.data = reinterpret_cast<const char*>(g_mapped_snapshot->data());
+  snapshot.raw_size = static_cast<int>(g_mapped_snapshot->length());
+  v8::V8::SetSnapshotDataBlob(&snapshot);
+#endif  // V8_USE_EXTERNAL_STARTUP_DATA
+
+  v8::V8::SetEntropySource(&GenerateEntropy);
+  v8::V8::Initialize();
+
+  v8_is_initialized = true;
+}
+
+// static
+void V8Initializer::GetV8ExternalSnapshotData(const char** natives_data_out,
+                                              int* natives_size_out,
+                                              const char** snapshot_data_out,
+                                              int* snapshot_size_out) {
+  if (!g_mapped_natives || !g_mapped_snapshot) {
+    *natives_data_out = *snapshot_data_out = NULL;
+    *natives_size_out = *snapshot_size_out = 0;
+    return;
+  }
+  *natives_data_out = reinterpret_cast<const char*>(g_mapped_natives->data());
+  *snapshot_data_out = reinterpret_cast<const char*>(g_mapped_snapshot->data());
+  *natives_size_out = static_cast<int>(g_mapped_natives->length());
+  *snapshot_size_out = static_cast<int>(g_mapped_snapshot->length());
+}
+
+}  // namespace gin
diff --git a/gin/v8_initializer.h b/gin/v8_initializer.h
new file mode 100644
index 0000000..ad3ed6e
--- /dev/null
+++ b/gin/v8_initializer.h
@@ -0,0 +1,57 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef GIN_V8_INITIALIZER_H_
+#define GIN_V8_INITIALIZER_H_
+
+#include "base/files/file.h"
+#include "gin/array_buffer.h"
+#include "gin/gin_export.h"
+#include "gin/public/isolate_holder.h"
+#include "gin/public/v8_platform.h"
+#include "v8/include/v8.h"
+
+namespace gin {
+
+class GIN_EXPORT V8Initializer {
+ public:
+  static const int kV8SnapshotBasePathKey;
+  static const char kNativesFileName[];
+  static const char kSnapshotFileName[];
+
+  // This should be called by IsolateHolder::Initialize().
+  static void Initialize(gin::IsolateHolder::ScriptMode mode,
+                         v8::ArrayBuffer::Allocator* allocator);
+
+  // Get address and size information for currently loaded snapshot.
+  // If no snapshot is loaded, the return values are null for addresses
+  // and 0 for sizes.
+  static void GetV8ExternalSnapshotData(const char** natives_data_out,
+                                        int* natives_size_out,
+                                        const char** snapshot_data_out,
+                                        int* snapshot_size_out);
+
+#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+
+  // Load V8 snapshot from user provided platform file descriptors.
+  // The offset and size arguments, if non-zero, specify the portions
+  // of the files to be loaded. This methods returns true on success
+  // (or if snapshot is already loaded), false otherwise.
+  static bool LoadV8SnapshotFromFD(base::PlatformFile natives_fd,
+                                   int64 natives_offset,
+                                   int64 natives_size,
+                                   base::PlatformFile snapshot_fd,
+                                   int64 snapshot_offset,
+                                   int64 snapshot_size);
+
+  // Load V8 snapshot from default resources. Returns true on success or
+  // snapshot is already loaded, false otherwise.
+  static bool LoadV8Snapshot();
+
+#endif  // V8_USE_EXTERNAL_STARTUP_DATA
+};
+
+}  // namespace gin
+
+#endif  // GIN_V8_INITIALIZER_H_
diff --git a/net/proxy/proxy_resolver_v8.cc b/net/proxy/proxy_resolver_v8.cc
index fcac10e..c41b190 100644
--- a/net/proxy/proxy_resolver_v8.cc
+++ b/net/proxy/proxy_resolver_v8.cc
@@ -18,6 +18,7 @@
 #include "base/synchronization/lock.h"
 #include "gin/array_buffer.h"
 #include "gin/public/isolate_holder.h"
+#include "gin/v8_initializer.h"
 #include "net/base/net_errors.h"
 #include "net/base/net_util.h"
 #include "net/log/net_log.h"
@@ -365,7 +366,7 @@ class SharedIsolateFactory {
       // Do one-time initialization for V8.
       if (!has_initialized_v8_) {
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
-        gin::IsolateHolder::LoadV8Snapshot();
+        gin::V8Initializer::LoadV8Snapshot();
 #endif
 
         gin::IsolateHolder::Initialize(
diff --git a/ppapi/proxy/pdf_resource.cc b/ppapi/proxy/pdf_resource.cc
index e9d3ae8..384fdc9 100644
--- a/ppapi/proxy/pdf_resource.cc
+++ b/ppapi/proxy/pdf_resource.cc
@@ -10,7 +10,7 @@
 #include "base/command_line.h"
 #include "base/metrics/histogram.h"
 #include "base/strings/utf_string_conversions.h"
-#include "gin/public/isolate_holder.h"
+#include "gin/v8_initializer.h"
 #include "ppapi/c/pp_errors.h"
 #include "ppapi/c/private/ppb_pdf.h"
 #include "ppapi/proxy/ppapi_messages.h"
@@ -210,8 +210,8 @@ void PDFResource::GetV8ExternalSnapshotData(const char** natives_data_out,
                                             int* natives_size_out,
                                             const char** snapshot_data_out,
                                             int* snapshot_size_out) {
-  gin::IsolateHolder::GetV8ExternalSnapshotData(natives_data_out,
-      natives_size_out, snapshot_data_out, snapshot_size_out);
+  gin::V8Initializer::GetV8ExternalSnapshotData(
+      natives_data_out, natives_size_out, snapshot_data_out, snapshot_size_out);
 }
 
 }  // namespace proxy