[Bindings] Create and use V8 context snapshots

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

Index: third_party/WebKit/Source/platform/bindings/V8PerIsolateData.cpp
diff --git a/third_party/WebKit/Source/platform/bindings/V8PerIsolateData.cpp b/third_party/WebKit/Source/platform/bindings/V8PerIsolateData.cpp
index 19eee733f61eadc76f64c8a9cac86fa1179742cb..50ba239777a82091f646b78d43fa0ea6ebf16340 100644
--- a/third_party/WebKit/Source/platform/bindings/V8PerIsolateData.cpp
+++ b/third_party/WebKit/Source/platform/bindings/V8PerIsolateData.cpp
@@ -27,6 +27,7 @@
 
 #include <memory>
 
+#include "platform/RuntimeEnabledFeatures.h"
 #include "platform/ScriptForbiddenScope.h"
 #include "platform/WebTaskRunner.h"
 #include "platform/bindings/DOMDataStore.h"
@@ -51,18 +52,29 @@ static void MicrotasksCompletedCallback(v8::Isolate* isolate) {
   V8PerIsolateData::From(isolate)->RunEndOfScopeTasks();
 }
 
-V8PerIsolateData::V8PerIsolateData(WebTaskRunner* task_runner)
-    : isolate_holder_(
+V8PerIsolateData::V8PerIsolateData(WebTaskRunner* task_runner,
+                                   intptr_t* table,
+                                   V8ContextMode v8_context_mode)
+    : v8_context_mode_(v8_context_mode),
+      isolate_holder_(
           task_runner ? task_runner->ToSingleThreadTaskRunner() : nullptr,
           gin::IsolateHolder::kSingleThread,
           IsMainThread() ? gin::IsolateHolder::kDisallowAtomicsWait
-                         : gin::IsolateHolder::kAllowAtomicsWait),
+                         : gin::IsolateHolder::kAllowAtomicsWait,
+          table,
+          v8_context_mode_ == V8ContextMode::kUseSnapshot ? &startup_data_
+                                                          : nullptr),
       string_cache_(WTF::WrapUnique(new StringCache(GetIsolate()))),
       private_property_(V8PrivateProperty::Create()),
       constructor_mode_(ConstructorMode::kCreateNewObject),
       use_counter_disabled_(false),
       is_handling_recursion_level_error_(false),
       is_reporting_exception_(false) {
+  // In case if failed to load the snapshot file
+  if (v8_context_mode_ == V8ContextMode::kUseSnapshot && !startup_data_.data) {
+    v8_context_mode_ = V8ContextMode::kDontUseSnapshot;
+  }
+
   // FIXME: Remove once all v8::Isolate::GetCurrent() calls are gone.
   GetIsolate()->Enter();
   GetIsolate()->AddBeforeCallEnteredCallback(&BeforeCallEnteredCallback);
@@ -71,6 +83,22 @@ V8PerIsolateData::V8PerIsolateData(WebTaskRunner* task_runner)
     g_main_thread_per_isolate_data = this;
 }
 
+V8PerIsolateData::V8PerIsolateData(intptr_t* reference_table)
+    : v8_context_mode_(V8ContextMode::kTakeSnapshot),
+      isolate_holder_(reference_table, nullptr),
+      string_cache_(WTF::WrapUnique(new StringCache(GetIsolate()))),
+      private_property_(V8PrivateProperty::Create()),
+      constructor_mode_(ConstructorMode::kCreateNewObject),
+      use_counter_disabled_(false),
+      is_handling_recursion_level_error_(false),
+      is_reporting_exception_(false) {
+  // FIXME: Remove once all v8::Isolate::GetCurrent() calls are gone.
+  // SnapshotCreator enters the isolate, so don't do it again.
+  GetIsolate()->AddBeforeCallEnteredCallback(&BeforeCallEnteredCallback);
+  GetIsolate()->AddMicrotasksCompletedCallback(&MicrotasksCompletedCallback);
+  g_main_thread_per_isolate_data = this;

[Yuki, 2017/06/01 14:15:51]

Let's avoid copy&pasting.  Then, we'll simply have
  if (IsMainThread())
    g_main_thread_per_isolate_data = this;
and it looks correct to me.  Currently we're unconditionally assuming that it's
on the main thread, and I think it's not good.

[peria, 2017/06/20 10:20:14]

I feel this routine should not be run on non-main threads.
Done.

+}
+
 V8PerIsolateData::~V8PerIsolateData() {}
 
 v8::Isolate* V8PerIsolateData::MainThreadIsolate() {
@@ -78,8 +106,24 @@ v8::Isolate* V8PerIsolateData::MainThreadIsolate() {
   return g_main_thread_per_isolate_data->GetIsolate();
 }
 
-v8::Isolate* V8PerIsolateData::Initialize(WebTaskRunner* task_runner) {
-  V8PerIsolateData* data = new V8PerIsolateData(task_runner);
+v8::Isolate* V8PerIsolateData::Initialize(WebTaskRunner* task_runner,
+                                          intptr_t* table,

[Yuki, 2017/06/01 14:15:51]

nit: s/table/reference_table/

[peria, 2017/06/20 10:20:14]

Done.

+                                          V8ContextMode context_mode) {
+  V8PerIsolateData* data = nullptr;

[Yuki, 2017/06/01 14:15:51]

Nice to have DCHECK(context_mode == kDontUseSnapshot || reference_table)?

[peria, 2017/06/20 10:20:14]

Done.

+  if (context_mode == V8ContextMode::kTakeSnapshot) {
+    CHECK(table);
+    data = new V8PerIsolateData(table);
+    v8::Isolate* isolate = data->GetIsolate();

[Yuki, 2017/06/01 14:15:51]

Better to share these lines of code with the latter case.

Otherwise, declaring V8PerIsolateData* data = nullptr; doesn't make sense.

[peria, 2017/06/20 10:20:14]

Done.

+    CHECK(isolate);
+    isolate->SetData(gin::kEmbedderBlink, data);
+    return isolate;
+  }
+
+  if (!RuntimeEnabledFeatures::v8ContextSnapshotEnabled()) {
+    context_mode = V8ContextMode::kDontUseSnapshot;
+    table = nullptr;
+  }
+  data = new V8PerIsolateData(task_runner, table, context_mode);
   v8::Isolate* isolate = data->GetIsolate();
   isolate->SetData(gin::kEmbedderBlink, data);
   return isolate;
@@ -163,6 +207,14 @@ v8::Local<v8::FunctionTemplate> V8PerIsolateData::FindOrCreateOperationTemplate(
 v8::Local<v8::FunctionTemplate> V8PerIsolateData::FindInterfaceTemplate(
     const DOMWrapperWorld& world,
     const void* key) {
+  if (GetV8ContextMode() == V8ContextMode::kTakeSnapshot) {
+    auto& map = interface_template_map_for_v8_snapshot_;
+    auto result = map.find(key);
+    if (result != map.end())
+      return result->value.Get(GetIsolate());
+    return v8::Local<v8::FunctionTemplate>();
+  }
+
   auto& map = SelectInterfaceTemplateMap(world);
   auto result = map.find(key);
   if (result != map.end())
@@ -174,8 +226,18 @@ void V8PerIsolateData::SetInterfaceTemplate(
     const DOMWrapperWorld& world,
     const void* key,
     v8::Local<v8::FunctionTemplate> value) {
-  auto& map = SelectInterfaceTemplateMap(world);
-  map.insert(key, v8::Eternal<v8::FunctionTemplate>(GetIsolate(), value));
+  if (GetV8ContextMode() == V8ContextMode::kTakeSnapshot) {
+    auto& map = interface_template_map_for_v8_snapshot_;
+    map.insert(key, CopyablePersistent(GetIsolate(), value));
+  } else {
+    auto& map = SelectInterfaceTemplateMap(world);
+    map.insert(key, v8::Eternal<v8::FunctionTemplate>(GetIsolate(), value));
+  }
+}
+
+void V8PerIsolateData::ClearPersistentsForV8Snapshot() {
+  interface_template_map_for_v8_snapshot_.clear();
+  private_property_.reset();
 }
 
 const v8::Eternal<v8::Name>* V8PerIsolateData::FindOrCreateEternalNameCache(