DevTools: Throttle Screencast on slow connections (Blink side)

Source/devtools/front_end/screencast/ScreencastView.js

Index: Source/devtools/front_end/screencast/ScreencastView.js
diff --git a/Source/devtools/front_end/screencast/ScreencastView.js b/Source/devtools/front_end/screencast/ScreencastView.js
index e3ab435ea83c1493fec2e11d66b86a0f775ce387..882857c17fc8322dd59d34be3d1936243f79d76f 100644
--- a/Source/devtools/front_end/screencast/ScreencastView.js
+++ b/Source/devtools/front_end/screencast/ScreencastView.js
@@ -153,6 +153,9 @@ WebInspector.ScreencastView.prototype = {
         this._scrollOffsetX = metadata.scrollOffsetX;
         this._scrollOffsetY = metadata.scrollOffsetY;
 
+        if (event.data.frameNumber)
+            this._target.pageAgent().screencastFrameAck(event.data.frameNumber);
+
         var deviceSizeRatio = metadata.deviceHeight / metadata.deviceWidth;
         var dimensionsCSS = this._viewportDimensions();