[DevTools] Move PNG encoding from UI to worker thread.

content/browser/devtools/protocol/page_handler.h

Index: content/browser/devtools/protocol/page_handler.h
diff --git a/content/browser/devtools/protocol/page_handler.h b/content/browser/devtools/protocol/page_handler.h
index a0b05452142839a12cc0d85c0af92ae65ac1921b..9f56d0bf6a6e49dac447ccc7b7141c6932ab5b3d 100644
--- a/content/browser/devtools/protocol/page_handler.h
+++ b/content/browser/devtools/protocol/page_handler.h
@@ -90,11 +90,11 @@ class PageHandler {
 
   void NotifyScreencastVisibility(bool visible);
   void InnerSwapCompositorFrame();
-  void ScreencastFrameCaptured(const std::string& format,
-                               int quality,
-                               const cc::CompositorFrameMetadata& metadata,
+  void ScreencastFrameCaptured(const cc::CompositorFrameMetadata& metadata,
                                const SkBitmap& bitmap,
                                ReadbackResponse response);
+  void ScreencastFrameEncoded(const cc::CompositorFrameMetadata& metadata,
+                              const std::string& data);
 
   void ScreenshotCaptured(
       scoped_refptr<DevToolsProtocol::Command> command,