Explicitly clear the image in the first updateImage() call

third_party/WebKit/Source/core/loader/resource/ImageResource.h

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller <mueller@kde.org>
     Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
     Copyright (C) 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.
 
     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Library General Public
     License as published by the Free Software Foundation; either
     version 2 of the License, or (at your option) any later version.
 
     This library is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Library General Public License for more details.
 
     You should have received a copy of the GNU Library General Public License
     along with this library; see the file COPYING.LIB.  If not, write to
     the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
     Boston, MA 02110-1301, USA.
 */
 
 #ifndef ImageResource_h
 #define ImageResource_h
 
 #include "core/CoreExport.h"
 #include "core/fetch/Resource.h"
+#include "core/loader/resource/ImageResourceContent.h"
 #include "core/loader/resource/ImageResourceInfo.h"
 #include "core/loader/resource/MultipartImageResourceParser.h"
 #include "platform/Timer.h"
 #include "platform/heap/Handle.h"
 #include <memory>
 
 namespace blink {
 
 class FetchRequest;
 class ImageResourceContent;
@@ skipping 84 matching lines @@
 
   bool hasClientsOrObservers() const override;
 
   void updateImageAndClearBuffer();
 
   void checkNotify() override;
 
   void destroyDecodedDataIfPossible() override;
   void destroyDecodedDataForFailedRevalidation() override;
 
+  // When UpdateImageOption is UpdateImage but this is the first
+  // updateImage() call, then ClearAndUpdateImage is used instead to enforce
+  // new image creation.
+  void updateImage(PassRefPtr<SharedBuffer>,
+                   ImageResourceContent::UpdateImageOption,
+                   bool allDataReceived);
   void flushImageIfNeeded(TimerBase*);
 
   bool shouldReloadBrokenPlaceholder() const {
     return m_isPlaceholder && willPaintBrokenImage();
   }
 
   bool willPaintBrokenImage() const;
 
   Member<ImageResourceContent> m_content;
 
+  // Indicates whether updateImage() is called for this resource, or for this
+  // part (in case of multipart images), and is used for enforcing creation of
+  // new blink::Image in ImageResourceContent for the first updateImage().
+  bool m_isUpdateImageCalled = false;

[kouhei (in TOK), 2016/12/19 01:32:04]

This flag name is quite confusing, as onePartIn~() also updates this.
Would inverting this flag & renaming this to "m_shouldEnforceClearImage" make
sense?

Would you document somewhere why we have this
ImageResourceContent::ClearImageOption in the first place?

[hiroshige, 2016/12/27 23:25:31]

Done in Patch Set 10.
Done (in https://codereview.chromium.org/2587503002/ Patch Set 6).

+
   // TODO(hiroshige): move |m_devicePixelRatioHeaderValue| and
   // |m_hasDevicePixelRatioHeaderValue| to ImageResourceContent and update
   // it via ImageResourceContent::updateImage().
   float m_devicePixelRatioHeaderValue;
 
   Member<MultipartImageResourceParser> m_multipartParser;
   MultipartParsingState m_multipartParsingState =
       MultipartParsingState::WaitingForFirstPart;
   bool m_hasDevicePixelRatioHeaderValue;
 
   // Indicates if the ImageResource is currently scheduling a reload, e.g.
   // because reloadIfLoFi() was called.
   bool m_isSchedulingReload;
 
   // Indicates if this ImageResource is either attempting to load a placeholder
   // image, or is a (possibly broken) placeholder image.
   bool m_isPlaceholder;
 
   Timer<ImageResource> m_flushTimer;
   double m_lastFlushTime = 0.;
 };
 
 DEFINE_RESOURCE_TYPE_CASTS(Image);
 
 }  // namespace blink
 
 #endif