Refactor DrawingRecorders to check for cached drawings earlier

Source/web/PageWidgetDelegate.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 77 matching lines @@
 
         IntRect dirtyRect(rect);
         FrameView* view = root.view();
         if (view) {
             ClipRecorder clipRecorder(paintContext, root, DisplayItem::PageWidgetDelegateClip, LayoutRect(dirtyRect));
 
             view->paint(&paintContext, dirtyRect);
             if (overlays)
                 overlays->paintWebFrame(paintContext);
         } else {
-            DrawingRecorder drawingRecorder(paintContext, root, DisplayItem::PageWidgetDelegateBackgroundFallback, dirtyRect);
-            if (!drawingRecorder.canUseCachedDrawing())
+            if (!DrawingRecorder::useCachedDrawingIfPossible(paintContext, root, DisplayItem::PageWidgetDelegateBackgroundFallback)) {

[Xianzhu, 2015/07/03 01:24:42]

Nit: can use 'else if' to avoid indentation change.

[pdr., 2015/07/03 02:38:05]

Done.

+                DrawingRecorder drawingRecorder(paintContext, root, DisplayItem::PageWidgetDelegateBackgroundFallback, dirtyRect);
                 paintContext.fillRect(dirtyRect, Color::white);
+            }
         }
     }
     pictureBuilder.endRecording()->playback(canvas);
 }
 
 bool PageWidgetDelegate::handleInputEvent(PageWidgetEventHandler& handler, const WebInputEvent& event, LocalFrame* root)
 {
     switch (event.type) {
 
     // FIXME: WebKit seems to always return false on mouse events processing
@@ skipping 95 matching lines @@
 {
     return mainFrame.eventHandler().handleWheelEvent(PlatformWheelEventBuilder(mainFrame.view(), event));
 }
 
 bool PageWidgetEventHandler::handleTouchEvent(LocalFrame& mainFrame, const WebTouchEvent& event)
 {
     return mainFrame.eventHandler().handleTouchEvent(PlatformTouchEventBuilder(mainFrame.view(), event));
 }
 
 } // namespace blink