Mojo multiple command buffer support and sample

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

 // 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.
 
 import "mojo/services/gles2/command_buffer.mojom"
 import "mojo/services/public/interfaces/geometry/geometry.mojom"
 import "mojo/services/public/interfaces/input_events/input_events.mojom"
 
 module mojo {
 
 [Client=NativeViewportClient]
 interface NativeViewport {
   Create(Rect bounds);
   Show();
   Hide();
   Close();
   SetBounds(Rect bounds);
   CreateGLES2Context(CommandBuffer& gles2_client);
+  CreateOffscreenGLES2Context(CommandBuffer& gles2_client);

[darin (slow to review), 2014/08/13 04:44:25]

Is it necessary for this to be supplied by the NativeViewport? I could imagine a
use case for providing an app with access to GL but no access to the screen.
This might be used for compute tasks, etc. Access control is likely to be at the
per-interface level rather than at the per-method level.

Maybe this is something that could be changed later, but I'm curious if we
shouldn't separate these more from the start.

 };
 
 interface NativeViewportClient {
   OnCreated();
   OnBoundsChanged(Rect bounds);
   OnDestroyed() => ();
   OnEvent(Event event) => ();
 };
 
 }