VideoCaptureImpl cleanup: merge ctor+Init() and DeInit()+dtor.

content/renderer/media/video_capture_impl.h

Index: content/renderer/media/video_capture_impl.h
diff --git a/content/renderer/media/video_capture_impl.h b/content/renderer/media/video_capture_impl.h
index 419af4f749abcdd5a804cbed726de0b2b897f4ac..5df25bea7cfea0672bbffcf7c6a9e837dd39807f 100644
--- a/content/renderer/media/video_capture_impl.h
+++ b/content/renderer/media/video_capture_impl.h
@@ -48,14 +48,10 @@ class CONTENT_EXPORT VideoCaptureImpl
  public:
   ~VideoCaptureImpl() override;
 
-  VideoCaptureImpl(media::VideoCaptureSessionId session_id,
-                   VideoCaptureMessageFilter* filter);
-
-  // Start listening to IPC messages.
-  void Init();
-
-  // Stop listening to IPC messages.
-  void DeInit();
+  VideoCaptureImpl(
+      media::VideoCaptureSessionId session_id,
+      VideoCaptureMessageFilter* filter,
+      scoped_refptr<base::SingleThreadTaskRunner> io_task_runner);
 
   // Stop/resume delivering video frames to clients, based on flag |suspend|.
   void SuspendCapture(bool suspend);
@@ -198,7 +194,7 @@ class CONTENT_EXPORT VideoCaptureImpl
   VideoCaptureState state_;
 
   // IO message loop reference for checking correct class operation.
-  scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
+  const scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
 
   // WeakPtrFactory pointing back to |this| object, for use with
   // media::VideoFrames constructed in OnBufferReceived() from buffers cached