Screen Video Capture: Implement suspend optimization.

content/browser/media/capture/aura_window_capture_machine.h

Index: content/browser/media/capture/aura_window_capture_machine.h
diff --git a/content/browser/media/capture/aura_window_capture_machine.h b/content/browser/media/capture/aura_window_capture_machine.h
index 848c3251de8fd35497f52e36c0fe63ec5f27940d..ff2334398dbc580dfe8f6cb3eba52242951cb511 100644
--- a/content/browser/media/capture/aura_window_capture_machine.h
+++ b/content/browser/media/capture/aura_window_capture_machine.h
@@ -43,6 +43,8 @@ class AuraWindowCaptureMachine
   void Start(const scoped_refptr<media::ThreadSafeCaptureOracle>& oracle_proxy,
              const media::VideoCaptureParams& params,
              const base::Callback<void(bool)> callback) override;
+  void Suspend() override;
+  void Resume() override;
   void Stop(const base::Closure& callback) override;
   void MaybeCaptureForRefresh() override;
 
@@ -66,6 +68,8 @@ class AuraWindowCaptureMachine
   bool InternalStart(
       const scoped_refptr<media::ThreadSafeCaptureOracle>& oracle_proxy,
       const media::VideoCaptureParams& params);
+  void InternalSuspend();
+  void InternalResume();
   void InternalStop(const base::Closure& callback);
 
   // Captures a frame. |event_time| is provided by the compositor, or is null
@@ -126,6 +130,10 @@ class AuraWindowCaptureMachine
   // screen from sleeping for the drive-by web.
   std::unique_ptr<device::PowerSaveBlocker> power_save_blocker_;
 
+  // False while frame capture has been suspended. All other aspects of the
+  // machine are maintained.
+  bool frame_capture_active_;
+
   // WeakPtrs are used for the asynchronous capture callbacks passed to external
   // modules.  They are only valid on the UI thread and become invalidated
   // immediately when InternalStop() is called to ensure that no more captured