[chrome.displaySource] Add common functionality to base video encoder.

extensions/renderer/api/display_source/wifi_display/wifi_display_video_encoder.h

Index: extensions/renderer/api/display_source/wifi_display/wifi_display_video_encoder.h
diff --git a/extensions/renderer/api/display_source/wifi_display/wifi_display_video_encoder.h b/extensions/renderer/api/display_source/wifi_display/wifi_display_video_encoder.h
index db5b642490f5c9279819cb8054d95a3001acc0a1..ec17ef69b7582c39d09b8859092ae475916c1962 100644
--- a/extensions/renderer/api/display_source/wifi_display/wifi_display_video_encoder.h
+++ b/extensions/renderer/api/display_source/wifi_display/wifi_display_video_encoder.h
@@ -57,17 +57,25 @@ class WiFiDisplayVideoEncoder : public WiFiDisplayMediaEncoder {
   // Encodes the given raw frame. The resulting encoded frame is passed
   // as an |encoded_callback|'s argument which is set via 'SetCallbacks'
   // method.
-  virtual void InsertRawVideoFrame(
-      const scoped_refptr<media::VideoFrame>& video_frame,
-      base::TimeTicks reference_time) = 0;
+  void InsertRawVideoFrame(const scoped_refptr<media::VideoFrame>& video_frame,
+                           base::TimeTicks reference_time);
 
   // Requests the next encoded frame to be an instantaneous decoding refresh
   // (IDR) picture.
-  virtual void RequestIDRPicture() = 0;
+  void RequestIDRPicture();
 
  protected:
-  WiFiDisplayVideoEncoder();
+  explicit WiFiDisplayVideoEncoder(
+      scoped_refptr<base::SingleThreadTaskRunner> media_task_runner);
   ~WiFiDisplayVideoEncoder() override;
+
+  virtual void InsertFrameOnMediaThread(
+      scoped_refptr<media::VideoFrame> video_frame,
+      base::TimeTicks reference_time,
+      bool send_idr) = 0;
+
+  scoped_refptr<base::SingleThreadTaskRunner> media_task_runner_;
+  bool send_idr_;
 };
 
 }  // namespace extensions