Add power monitoring to the Cast VideoToolbox encoder.

media/cast/sender/h264_vt_encoder.h

Index: media/cast/sender/h264_vt_encoder.h
diff --git a/media/cast/sender/h264_vt_encoder.h b/media/cast/sender/h264_vt_encoder.h
index 756571c0c10bb804ae46e26556bfeb2c248ea4f0..f197c3765c70d420b09f55cc178769ab7415afb3 100644
--- a/media/cast/sender/h264_vt_encoder.h
+++ b/media/cast/sender/h264_vt_encoder.h
@@ -6,6 +6,7 @@
 #define MEDIA_CAST_SENDER_H264_VT_ENCODER_H_
 
 #include "base/mac/scoped_cftyperef.h"
+#include "base/power_monitor/power_observer.h"
 #include "base/threading/thread_checker.h"
 #include "media/base/mac/videotoolbox_glue.h"
 #include "media/cast/sender/size_adaptable_video_encoder_base.h"
@@ -17,8 +18,10 @@ namespace cast {
 // VideoToolbox implementation of the media::cast::VideoEncoder interface.
 // VideoToolbox makes no guarantees that it is thread safe, so this object is
 // pinned to the thread on which it is constructed. Supports changing frame
-// sizes directly.
-class H264VideoToolboxEncoder : public VideoEncoder {
+// sizes directly. Implements the base::PowerObserver interface to reset the
+// compression session when the host process is suspended.
+class H264VideoToolboxEncoder : public VideoEncoder,
+                                public base::PowerObserver {
   typedef CoreMediaGlue::CMSampleBufferRef CMSampleBufferRef;
   typedef VideoToolboxGlue::VTCompressionSessionRef VTCompressionSessionRef;
   typedef VideoToolboxGlue::VTEncodeInfoFlags VTEncodeInfoFlags;
@@ -45,6 +48,10 @@ class H264VideoToolboxEncoder : public VideoEncoder {
   scoped_ptr<VideoFrameFactory> CreateVideoFrameFactory() override;
   void EmitFrames() override;
 
+  // base::PowerObserver
+  void OnSuspend() override;
+  void OnResume() override;
+
  private:
   // VideoFrameFactory tied to the VideoToolbox encoder.
   class VideoFrameFactoryImpl;