Refactor DrawingRecorders to check for cached drawings earlier

Source/web/PageOverlayTest.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "web/PageOverlay.h"
 
 #include "core/frame/FrameView.h"
 #include "core/layout/LayoutView.h"
 #include "platform/graphics/Color.h"
@@ skipping 87 matching lines @@
 
 // WebPageOverlay that uses the underlying blink::GraphicsContext to paint a
 // solid color.
 class PrivateGraphicsContextOverlay : public WebPageOverlay {
 public:
     PrivateGraphicsContextOverlay(Color color) : m_color(color) { }
 
     void paintPageOverlay(WebGraphicsContext* context, const WebSize& size) override
     {
         GraphicsContext& graphicsContext = toWebGraphicsContextImpl(context)->graphicsContext();
-        FloatRect rect(0, 0, size.width, size.height);
-        DrawingRecorder drawingRecorder(graphicsContext, *this, DisplayItem::PageOverlay, rect);
-        if (!drawingRecorder.canUseCachedDrawing())
+        if (!DrawingRecorder::useCachedDrawingIfPossible(graphicsContext, *this, DisplayItem::PageOverlay)) {

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

Nit:

'if (DrawingRecorder::...)
  return;'
seems better.

[pdr., 2015/07/03 02:38:04]

I agree. Done.

+            FloatRect rect(0, 0, size.width, size.height);
+            DrawingRecorder drawingRecorder(graphicsContext, *this, DisplayItem::PageOverlay, rect);
             graphicsContext.fillRect(rect, m_color);
+        }
     }
 
     DisplayItemClient displayItemClient() const { return toDisplayItemClient(this); }
     String debugName() const { return "PrivateGraphicsContextOverlay"; }
 
 private:
     Color m_color;
 };
 
 template <bool(*getter)(), void(*setter)(bool)>
@@ skipping 109 matching lines @@
 }
 
 TEST_F(PageOverlayTest, PrivateGraphicsContextOverlay_AcceleratedCompositing_SlimmingPaint)
 {
     SlimmingPaintScope slimmingPaintEnabled(true);
     runPageOverlayTestWithAcceleratedCompositing<PrivateGraphicsContextOverlay>();
 }
 
 } // namespace
 } // namespace blink