Android: Throttle BeginFrame messages sent from the browser.

content/renderer/gpu/mailbox_output_surface.cc

 // Copyright (c) 2012 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 "content/renderer/gpu/mailbox_output_surface.h"
 
 #include "base/logging.h"
 #include "cc/output/compositor_frame.h"
 #include "cc/output/compositor_frame_ack.h"
 #include "cc/output/gl_frame_data.h"
@@ skipping 180 matching lines @@
     // the oldest texture we sent.
     uint32 texture_id = pending_textures_.front().texture_id;
     if (texture_id)
       context3d_->deleteTexture(texture_id);
     pending_textures_.pop_front();
   }
   CompositorOutputSurface::OnSwapAck(ack);
 }
 
 void MailboxOutputSurface::SwapBuffers(const ui::LatencyInfo&) {
+  DCHECK(GetNumAcksPending() < 2);
 }
 
 void MailboxOutputSurface::PostSubBuffer(gfx::Rect rect,
                                          const ui::LatencyInfo&) {
   NOTIMPLEMENTED()
       << "Partial swap not supported with composite-to-mailbox yet.";
 
   // The browser only copies damage correctly for two buffers in use.
   DCHECK(GetNumAcksPending() < 2);
 }
 
 void MailboxOutputSurface::ConsumeTexture(const TransferableFrame& frame) {
   DCHECK(!frame.mailbox.IsZero());
   if (frame.sync_point)
     context3d_->waitSyncPoint(frame.sync_point);
 
   context3d_->bindTexture(GL_TEXTURE_2D, frame.texture_id);
   context3d_->consumeTextureCHROMIUM(GL_TEXTURE_2D, frame.mailbox.name);
 }
 
 size_t MailboxOutputSurface::GetNumAcksPending() {
   DCHECK(pending_textures_.size());
   return pending_textures_.size() - 1;
 }
 
 }  // namespace content