Remove duplication of encoded image data

third_party/WebKit/Source/core/fetch/ImageResource.cpp

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Waldo Bastian (bastian@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
@@ skipping 105 matching lines @@
 
 void ImageResource::addObserver(ImageResourceObserver* observer)
 {
     willAddClientOrObserver();
 
     m_observers.add(observer);
 
     if (isCacheValidator())
         return;
 
-    if (m_data && !m_image && !errorOccurred()) {
-        createImage();
-        m_image->setData(m_data, true);
-    }
-
     if (m_image && !m_image->isNull()) {
         observer->imageChanged(this);
     }
 
     if (isLoaded()) {
         observer->imageNotifyFinished(this);
         if (m_observers.contains(observer)) {
             m_finishedObservers.add(observer);
             m_observers.remove(observer);
         }
@@ skipping 208 matching lines @@
 
     if (m_data)
         createImage();
 
     bool sizeAvailable = false;
 
     // Have the image update its data from its internal buffer.
     // It will not do anything now, but will delay decoding until
     // queried for info (like size or specific image frames).
     if (m_image)
         sizeAvailable = m_image->setData(m_data, allDataReceived);

[hiroshige, 2016/06/15 13:16:25]

Isn't it problematic if |setData(m_data)| is called here after we clear |m_data|
in finish()?

[hajimehoshi, 2016/06/16 09:43:20]

Actually |m_data| is null here after m_data.clear() at L390. In this case, is
encoded image data in |m_image| different from |m_data|? If so, why should we
call |setData| here?

[hajimehoshi, 2016/06/16 09:47:41]

s/In this case,/Aside from |m_data.clear()|,/

[hajimehoshi, 2016/06/17 09:25:15]

TBH I'm not confident this is OK. Let me check with DCHECK and bot tests.

 
     // Go ahead and tell our observers to try to draw if we have either
     // received all the data or the size is known. Each chunk from the
     // network causes observers to repaint, which will force that chunk
     // to decode.
     if (sizeAvailable || allDataReceived) {
         if (!m_image || m_image->isNull()) {
             if (!errorOccurred())
                 setStatus(DecodeError);
             clear();
@@ skipping 15 matching lines @@
 }
 
 void ImageResource::finish(double loadFinishTime)
 {
     if (m_multipartParser) {
         m_multipartParser->finish();
         if (m_data)
             updateImageAndClearBuffer();
     } else {
         updateImage(true);
+        m_data.clear();
     }
     Resource::finish(loadFinishTime);
 }
 
 void ImageResource::error(const ResourceError& error)
 {
     if (m_multipartParser)
         m_multipartParser->cancel();
     clear();
     Resource::error(error);
@@ skipping 88 matching lines @@
         m_image->setAnimationPolicy(newPolicy);
     }
 }
 
 void ImageResource::reloadIfLoFi(ResourceFetcher* fetcher)
 {
     if (!m_response.httpHeaderField("chrome-proxy").contains("q=low"))
         return;
     m_resourceRequest.setCachePolicy(WebCachePolicy::BypassingCache);
     m_resourceRequest.setLoFiState(WebURLRequest::LoFiOff);
-    if (isLoading())
+    if (isLoading()) {
         m_loader->cancel();
-    else
-        updateImageAndClearBuffer();
+    }
     setStatus(NotStarted);
     fetcher->startLoad(this);
 }
 
 void ImageResource::changedInRect(const blink::Image* image, const IntRect& rect)
 {
     if (!image || image != m_image)
         return;
     notifyObservers(&rect);
 }
@@ skipping 32 matching lines @@
     if (response().wasFetchedViaServiceWorker())
         return response().serviceWorkerResponseType() != WebServiceWorkerResponseTypeOpaque;
     if (!getImage()->currentFrameHasSingleSecurityOrigin())
         return false;
     if (passesAccessControlCheck(securityOrigin))
         return true;
     return !securityOrigin->taintsCanvas(response().url());
 }
 
 } // namespace blink