[gin] Add a v8::Platform implementation to allow for v8 posting tasks

gin/v8_platform.cc

+// Copyright 2014 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/public/v8_platform.h"
+
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/message_loop/message_loop_proxy.h"
+#include "base/threading/worker_pool.h"
+#include "gin/per_isolate_data.h"
+
+namespace gin {
+
+namespace {
+
+base::LazyInstance<V8Platform>::Leaky g_v8_platform = LAZY_INSTANCE_INITIALIZER;
+
+}  // namespace
+
+// static
+V8Platform* V8Platform::Get() { return g_v8_platform.Pointer(); }
+
+V8Platform::V8Platform() {}
+
+V8Platform::~V8Platform() {}
+
+void V8Platform::CallOnBackgroundThread(
+    v8::Task* task,
+    v8::Platform::ExpectedRuntime expected_runtime) {
+  base::WorkerPool::PostTask(
+      FROM_HERE,
+      base::Bind(&v8::Task::Run, base::Owned(task)),
+      expected_runtime == v8::Platform::kLongRunningTask);
+}
+
+void V8Platform::CallOnForegroundThread(v8::Isolate* isolate, v8::Task* task) {
+  PerIsolateData::From(isolate)->message_loop_proxy()->PostTask(
+      FROM_HERE, base::Bind(&v8::Task::Run, base::Owned(task)));
+}
+
+}  // namespace gin