Limit outstanding surface draw swaps to max_frames_pending.

content/browser/compositor/onscreen_display_client.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 "content/browser/compositor/onscreen_display_client.h"
 
 #include "base/debug/trace_event.h"
 #include "cc/output/output_surface.h"
 #include "cc/surfaces/surface_factory.h"
 #include "cc/surfaces/surface_manager.h"
 #include "content/common/host_shared_bitmap_manager.h"
 
 namespace content {
 
 OnscreenDisplayClient::OnscreenDisplayClient(
     scoped_ptr<cc::OutputSurface> output_surface,
     cc::SurfaceManager* manager,
     scoped_refptr<base::SingleThreadTaskRunner> task_runner)
     : output_surface_(output_surface.Pass()),
       display_(
           new cc::Display(this, manager, HostSharedBitmapManager::current())),
       task_runner_(task_runner),
       scheduled_draw_(false),
+      deferred_draw_(false),
+      pending_frames_(0),
       weak_ptr_factory_(this) {
 }
 
 OnscreenDisplayClient::~OnscreenDisplayClient() {
 }
 
 scoped_ptr<cc::OutputSurface> OnscreenDisplayClient::CreateOutputSurface() {
   DCHECK(output_surface_.get());
   return output_surface_.Pass();
 }
 
 void OnscreenDisplayClient::DisplayDamaged() {
-  if (scheduled_draw_)
+  if (scheduled_draw_ || deferred_draw_)
     return;
   TRACE_EVENT0("content", "OnscreenDisplayClient::DisplayDamaged");
+  if (pending_frames_ >= display_->GetMaxFramesPending()) {
+    deferred_draw_ = true;
+  } else {
+    ScheduleDraw();
+  }
+}
+
+void OnscreenDisplayClient::ScheduleDraw() {
+  DCHECK(!deferred_draw_);
+  DCHECK(!scheduled_draw_);
   scheduled_draw_ = true;
   task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&OnscreenDisplayClient::Draw, weak_ptr_factory_.GetWeakPtr()));
 }
 
 void OnscreenDisplayClient::Draw() {
   TRACE_EVENT0("content", "OnscreenDisplayClient::Draw");
   scheduled_draw_ = false;
   display_->Draw();
 }
 
+void OnscreenDisplayClient::DidSwapBuffers() {
+  pending_frames_++;
+}
+
+void OnscreenDisplayClient::DidSwapBuffersComplete() {
+  pending_frames_--;
+  if ((pending_frames_ < display_->GetMaxFramesPending()) && deferred_draw_) {
+    deferred_draw_ = false;
+    ScheduleDraw();
+  }
+}
+
 }  // namespace content