Refactor DrawingRecorders to check for cached drawings earlier

Source/platform/scroll/ScrollbarTheme.cpp

 /*
  * Copyright (C) 2011 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 197 matching lines @@
     }
     result.moveBy(-scrollbar->location());
     scrollbar->invalidateRect(result);
 }
 
 void ScrollbarTheme::paintScrollCorner(GraphicsContext* context, const DisplayItemClientWrapper& displayItemClient, const IntRect& cornerRect)
 {
     if (cornerRect.isEmpty())
         return;
 
-    DrawingRecorder recorder(*context, displayItemClient, DisplayItem::ScrollbarCorner, cornerRect);
-    if (recorder.canUseCachedDrawing())
+    if (DrawingRecorder::useCachedDrawingIfPossible(*context, displayItemClient, DisplayItem::ScrollbarCorner))
         return;
 
+    DrawingRecorder recorder(*context, displayItemClient, DisplayItem::ScrollbarCorner, cornerRect);
 #if OS(MACOSX)
     context->fillRect(cornerRect, Color::white);
 #else
     Platform::current()->themeEngine()->paint(context->canvas(), WebThemeEngine::PartScrollbarCorner, WebThemeEngine::StateNormal, WebRect(cornerRect), 0);
 #endif
 }
 
 bool ScrollbarTheme::shouldCenterOnThumb(ScrollbarThemeClient* scrollbar, const PlatformMouseEvent& evt)
 {
     return Platform::current()->scrollbarBehavior()->shouldCenterOnThumb(static_cast<WebScrollbarBehavior::Button>(evt.button()), evt.shiftKey(), evt.altKey());
@@ skipping 140 matching lines @@
         return DisplayItem::ScrollbarBackTrack;
     case ForwardTrackPart:
         return DisplayItem::ScrollbarForwardTrack;
     default:
         ASSERT_NOT_REACHED();
         return DisplayItem::ScrollbarBackTrack;
     }
 }
 
 } // namespace blink