[Bindings] Create and use V8 context snapshots

gin/public/isolate_holder.h

Index: gin/public/isolate_holder.h
diff --git a/gin/public/isolate_holder.h b/gin/public/isolate_holder.h
index 0d9cb3b39ef17561c090cf57d0f8dc916a67f0c7..6486c1fccce6cd4f8aa793af7a1e8cd9f2895748 100644
--- a/gin/public/isolate_holder.h
+++ b/gin/public/isolate_holder.h
@@ -53,13 +53,21 @@ class GIN_EXPORT IsolateHolder {
     kStableAndExperimentalV8Extras,
   };
 
+  enum V8ContextMode {
+    kDefault,
+    kTakeSnapshot,
+    kUseSnapshot,
+  };
+
   explicit IsolateHolder(
       scoped_refptr<base::SingleThreadTaskRunner> task_runner);
   IsolateHolder(scoped_refptr<base::SingleThreadTaskRunner> task_runner,
                 AccessMode access_mode);
   IsolateHolder(scoped_refptr<base::SingleThreadTaskRunner> task_runner,
                 AccessMode access_mode,
-                AllowAtomicsWaitMode atomics_wait_mode);
+                AllowAtomicsWaitMode atomics_wait_mode,
+                intptr_t*,
+                V8ContextMode);
   ~IsolateHolder();
 
   // Should be invoked once before creating IsolateHolder instances to
@@ -75,6 +83,7 @@ class GIN_EXPORT IsolateHolder {
                          v8::ArrayBuffer::Allocator* allocator);
 
   v8::Isolate* isolate() { return isolate_; }
+  v8::SnapshotCreator* snapshot_creator() { return snapshot_creator_.get(); }
 
   // The implementations of Object.observe() and Promise enqueue v8 Microtasks
   // that should be executed just before control is returned to the message
@@ -100,12 +109,17 @@ class GIN_EXPORT IsolateHolder {
     return isolate_memory_dump_provider_.get();
   }
 
+  V8ContextMode v8_context_mode() const { return v8_context_mode_; }
+
  private:
   v8::Isolate* isolate_;
+  std::unique_ptr<v8::SnapshotCreator> snapshot_creator_;
   std::unique_ptr<PerIsolateData> isolate_data_;
   std::unique_ptr<RunMicrotasksObserver> task_observer_;
   std::unique_ptr<V8IsolateMemoryDumpProvider> isolate_memory_dump_provider_;
   AccessMode access_mode_;
+  v8::StartupData startup_data_;
+  V8ContextMode v8_context_mode_;
 
   DISALLOW_COPY_AND_ASSIGN(IsolateHolder);
 };