Teach SkyShell.apk to stop posting frames when not visible

sky/shell/ui/engine.h

 // Copyright 2015 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 SKY_SHELL_UI_ENGINE_H_
 #define SKY_SHELL_UI_ENGINE_H_
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 53 matching lines @@
   // SkyEngine implementation:
   void OnViewportMetricsChanged(ViewportMetricsPtr metrics) override;
   void OnInputEvent(InputEventPtr event) override;
 
   void RunFromNetwork(const mojo::String& url) override;
   void RunFromFile(const mojo::String& main,
                    const mojo::String& package_root) override;
   void RunFromSnapshot(const mojo::String& path) override;
   void RunFromBundle(const mojo::String& path) override;
 
+  void OnActivityPaused() override;
+  void OnActivityResumed() override;
+
   // SkyViewClient methods:
   void ScheduleFrame() override;
   void DidCreateIsolate(Dart_Isolate isolate) override;
 
   // Services methods:
   mojo::NavigatorHost* NavigatorHost() override;
 
   // NavigatorHost methods:
   void RequestNavigate(mojo::Target target,
                        mojo::URLRequestPtr request) override;
   void DidNavigateLocally(const mojo::String& url) override;
   void RequestNavigateHistory(int32_t delta) override;
 
   void RunFromLibrary(const std::string& name);
   void RunFromSnapshotStream(const std::string& name,
                              mojo::ScopedDataPipeConsumerHandle snapshot);
 
+  void StopAnimator();
+  void StartAnimatorIfPossible();
+
   Config config_;
   scoped_ptr<Animator> animator_;
 
   mojo::asset_bundle::AssetBundlePtr root_bundle_;
   scoped_ptr<blink::DartLibraryProvider> dart_library_provider_;
   std::unique_ptr<blink::SkyView> sky_view_;
 
   gfx::Size physical_size_;
   blink::SkyDisplayMetrics display_metrics_;
   mojo::Binding<SkyEngine> binding_;
 
+  bool activity_running_;
+  bool have_surface_;
+
   base::WeakPtrFactory<Engine> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Engine);
 };
 
 }  // namespace shell
 }  // namespace sky
 
 #endif  // SKY_SHELL_UI_ENGINE_H_