Preparation for enabling slimming paint synchronized painting

third_party/WebKit/Source/web/WebGraphicsContextImpl.h

 // 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.
 
 #ifndef WebGraphicsContextImpl_h
 #define WebGraphicsContextImpl_h
 
 #include "platform/graphics/paint/DisplayItem.h"
+#include "platform/graphics/paint/DisplayItemCacheSkipper.h"
 #include "platform/graphics/paint/DisplayItemClient.h"
 #include "public/web/WebGraphicsContext.h"
 #include "wtf/OwnPtr.h"
 
 namespace blink {
 
 class DrawingRecorder;
 class GraphicsContext;
 
 // Wraps a blink::GraphicsContext.
 // Internal consumers can extract the underlying context (via WebGraphicsContextImpl).
 // External consumers can make a single drawing using a WebCanvas.
 class WebGraphicsContextImpl : public WebGraphicsContext {
 public:
     WebGraphicsContextImpl(GraphicsContext&, const DisplayItemClientWrapper&, DisplayItem::Type);
     ~WebGraphicsContextImpl();
     GraphicsContext& graphicsContext() { return m_graphicsContext; }
 
     // blink::WebGraphicsContext
     WebCanvas* beginDrawing(const WebFloatRect& bounds) override;
     void endDrawing() override;
 
 private:
     GraphicsContext& m_graphicsContext;
     DisplayItemClientWrapper m_client;
     DisplayItem::Type m_type;
     OwnPtr<DrawingRecorder> m_drawingRecorder;
+    DisplayItemCacheSkipper m_cacheSkipper;

[pdr., 2015/10/29 04:06:10]

I wouldn't expect WebGraphicsContext to disable caching. Is this just for
PageOverlay? If so, can we explicitly disable caching in PageOverlay?

[Xianzhu, 2015/10/29 04:22:01]

WebGraphicsContext seems to expect that no cache exists (in
WebGraphicsContextImpl::beginDrawing():
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...)

I encountered assertion failure in WebGraphicsContextImpl::beginDrawing().

Should we change beginDrawing() to allow caching? 

[chrishtr, 2015/10/29 20:22:46]

Let's delete the beginDrawing()/endDrawing() methods and inline the skipper and
DrawingRecorder in WebViewImpl::paintPageOverlay. That's the only call site.
Also it's safe to use toWebGraphicsContextImpl() there to cast since the only
call site uses that class. InspectorOverlay does the same thing already.

Please also break some of these changes into new patches.

 #ifndef NDEBUG
     bool m_hasBegunDrawing;
 #endif
 };
 
 // Source/web/ assumes that WebGraphicsContextImpl is the only implementation.
 DEFINE_TYPE_CASTS(WebGraphicsContextImpl, WebGraphicsContext, webGraphicsContext, true, true);
 
 } // namespace blink
 
 #endif