bindings: Bind V8's snapshot file to Blink's snapshot

Before this CL, Blink's snapshot was created from scratch, and it meant
something in V8's snapshot could be missed.

After this CL, v8_context_snapshot_gerator will create a snapshot
file which involves all information in V8's snapshot file.

This change is a preparation to remove V8's snapshot file from binded
resources of Chromium.



Bug: 750176
Change-Id: I18050cc8131cd836a7b100c8b28cf0148c4a7f4f
Reviewed-on: https://chromium-review.googlesource.com/656866
Commit-Queue: Hitoshi Yoshida <peria@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#502494}

gin/isolate_holder.cc

@@ -75,10 +75,19 @@ IsolateHolder::IsolateHolder(
 
 IsolateHolder::IsolateHolder(const intptr_t* reference_table,
                              v8::StartupData* existing_blob)
-    : snapshot_creator_(
-          new v8::SnapshotCreator(reference_table, existing_blob)),
-      isolate_(snapshot_creator_->GetIsolate()),
-      access_mode_(AccessMode::kSingleThread) {
+    : access_mode_(AccessMode::kSingleThread) {
+  CHECK(existing_blob);
+
+  v8::StartupData unused_natives;
+  V8Initializer::GetV8ExternalSnapshotData(&unused_natives, existing_blob);
+  if (!existing_blob->data) {
+    existing_blob = nullptr;
+  }
+
+  snapshot_creator_.reset(
+      new v8::SnapshotCreator(reference_table, existing_blob));
+  isolate_ = snapshot_creator_->GetIsolate();
+
   SetUp(nullptr);
 }
 

third_party/WebKit/Source/platform/bindings/V8PerIsolateData.cpp

@@ -39,6 +39,7 @@
 #include "public/platform/Platform.h"
 #include "public/web/WebKit.h"
 #include "v8/include/v8-debug.h"
+#include "v8/include/v8.h"
 
 namespace blink {
 
@@ -97,7 +98,7 @@ V8PerIsolateData::V8PerIsolateData(
 // main thread.
 V8PerIsolateData::V8PerIsolateData(const intptr_t* reference_table)
     : v8_context_snapshot_mode_(V8ContextSnapshotMode::kTakeSnapshot),
-      isolate_holder_(reference_table, nullptr),
+      isolate_holder_(reference_table, &startup_data_),
       interface_template_map_for_v8_context_snapshot_(GetIsolate()),
       string_cache_(WTF::WrapUnique(new StringCache(GetIsolate()))),
       private_property_(V8PrivateProperty::Create()),

third_party/WebKit/Source/platform/bindings/V8PerIsolateData.h

@@ -288,8 +288,7 @@ class PLATFORM_EXPORT V8PerIsolateData {
   HashMap<const void*, Vector<v8::Eternal<v8::Name>>> eternal_name_cache_;
 
   // Members required for the V8 context snapshot.
-  // v8::Context is created from this blob data image. This needs to be
-  // instantiated before |isolate_holder_| gets instantiated.
+  // v8::Context is created from this blob data image.
   v8::StartupData startup_data_;
   // When taking a V8 context snapshot, we can't keep V8 objects with eternal
   // handles. So we use a special interface map that doesn't use eternal handles