Mojo multiple command buffer support and sample

mojo/services/public/interfaces/native_viewport/native_viewport.mojom

Index: mojo/services/public/interfaces/native_viewport/native_viewport.mojom
diff --git a/mojo/services/public/interfaces/native_viewport/native_viewport.mojom b/mojo/services/public/interfaces/native_viewport/native_viewport.mojom
index b168104a704be40bcf438f5d1c68b0ee557c74c4..c1a9742a063c8ec44f31558c04b41cc2906e5eee 100644
--- a/mojo/services/public/interfaces/native_viewport/native_viewport.mojom
+++ b/mojo/services/public/interfaces/native_viewport/native_viewport.mojom
@@ -15,13 +15,12 @@ interface NativeViewport {
   Hide();
   Close();
   SetBounds(Rect bounds);
-  CreateGLES2Context(CommandBuffer& gles2_client);
 };
 
 interface NativeViewportClient {
-  OnCreated();
+  OnCreated(uint64 native_viewport_id);
   OnBoundsChanged(Rect bounds);
-  OnDestroyed() => ();
+  OnDestroyed();
   OnEvent(Event event) => ();
 };