Add signalSyncPoint to the WebGraphicsContext3D command buffer impls.

cc/resources/sync_point_helper.h

Index: cc/resources/sync_point_helper.h
diff --git a/cc/resources/sync_point_helper.h b/cc/resources/sync_point_helper.h
new file mode 100644
index 0000000000000000000000000000000000000000..c342069bc7e2b70f4e6a676c2f7192d610f2f29e
--- /dev/null
+++ b/cc/resources/sync_point_helper.h
@@ -0,0 +1,36 @@
+// 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 CC_RESOURCES_SYNC_POINT_HELPER_H_
+#define CC_RESOURCES_SYNC_POINT_HELPER_H_
+
+#include "base/callback.h"
+#include "cc/base/cc_export.h"
+
+namespace WebKit { class WebGraphicsContext3D; }
+
+namespace cc {
+
+class CC_EXPORT SyncPointHelper {
+ public:
+  // Requests a callback to |closure| when the |sync_point| is reached by the
+  // |context3d|.
+  //
+  // If the |context3d| is destroyed or lost before the callback fires, then
+  // AbortBecauseDidLoseOrDestroyContext() must be called to clean up the
+  // callback's resources.
+  static void SignalSyncPoint(
+      WebKit::WebGraphicsContext3D* context3d,
+      unsigned sync_point,
+      const base::Closure& closure);
+
+ private:
+  SyncPointHelper();
+
+  DISALLOW_COPY_AND_ASSIGN(SyncPointHelper);
+};
+
+}  // namespace cc
+
+#endif  // CC_RESOURCES_SYNC_POINT_HELPER_H_