Reload image bypassing the cache

Source/core/loader/ImageLoader.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2009, 2010 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.
  *
@@ skipping 82 matching lines @@
             // loader has been GCed, but not yet lazily swept & finalized
             // (when this task's loader reference will be cleared.)
             //
             // Handle this transient condition by explicitly checking here
             // before going ahead with the update operation. Unsafe to do it
             // if so, as the objects that the loader refers to may have been
             // finalized by this time.
             if (Heap::willObjectBeLazilySwept(m_loader))
                 return;
 #endif
-            m_loader->doUpdateFromElement(m_shouldBypassMainWorldCSP, m_updateBehavior);
+            m_loader->doUpdateFromElement(m_shouldBypassMainWorldCSP, m_updateBehavior, false);

[Yoav Weiss, 2015/04/29 06:13:24]

This shouldn't be a boolean, but an enum. That way we can tell what it does from
when calling the method.

Also - is the bypassCache state always false for images that are asynchronously
loaded? Can you explain the logic?

         }
     }
 
     void clearLoader()
     {
         m_loader = 0;
     }
 
     WeakPtr<Task> createWeakPtr()
     {
@@ skipping 116 matching lines @@
 }
 
 inline void ImageLoader::enqueueImageLoadingMicroTask(UpdateFromElementBehavior updateBehavior)
 {
     OwnPtr<Task> task = Task::create(this, updateBehavior);
     m_pendingTask = task->createWeakPtr();
     Microtask::enqueueMicrotask(task.release());
     m_loadDelayCounter = IncrementLoadEventDelayCount::create(m_element->document());
 }
 
-void ImageLoader::doUpdateFromElement(BypassMainWorldBehavior bypassBehavior, UpdateFromElementBehavior updateBehavior)
+void ImageLoader::doUpdateFromElement(BypassMainWorldBehavior bypassBehavior, UpdateFromElementBehavior updateBehavior, bool bypassCache)
 {
     // FIXME: According to
     // http://www.whatwg.org/specs/web-apps/current-work/multipage/embedded-content.html#the-img-element:the-img-element-55
     // When "update image" is called due to environment changes and the load fails, onerror should not be called.
     // That is currently not the case.
     //
     // We don't need to call clearLoader here: Either we were called from the
     // task, or our caller updateFromElement cleared the task's loader (and set
     // m_pendingTask to null).
     m_pendingTask.clear();
     // Make sure to only decrement the count when we exit this function
     OwnPtr<IncrementLoadEventDelayCount> loadDelayCounter;
     loadDelayCounter.swap(m_loadDelayCounter);
 
     Document& document = m_element->document();
     if (!document.isActive())
         return;
 
     AtomicString imageSourceURL = m_element->imageSourceURL();
     KURL url = imageSourceToKURL(imageSourceURL);
     ResourcePtr<ImageResource> newImage = 0;
     RefPtrWillBeRawPtr<Element> protectElement(m_element.get());
     if (!url.isNull()) {
         // Unlike raw <img>, we block mixed content inside of <picture> or <img srcset>.
         ResourceLoaderOptions resourceLoaderOptions = ResourceFetcher::defaultResourceOptions();
         ResourceRequest resourceRequest(url);
         resourceRequest.setFetchCredentialsMode(WebURLRequest::FetchCredentialsModeSameOrigin);
+        if (bypassCache)
+            resourceRequest.setCachePolicy(ResourceRequestCachePolicy::ReloadBypassingCache);

[Nate Chapin, 2015/04/30 20:59:41]

I'm not thrilled with the need to bypass the cache when loading the real image
contents. That seems like it could break if LoFi images are enabled, then
disabled. Perhaps LoFi images could include Cache-Control: headers?

[megjablon, 2015/04/30 22:00:54]

We discussed using no-store, but want LoFi images to be cached since the goal of
Data Saver is to be conservative with users' data. We want to bypass the cache
and load the original image only when the user explicitly asks to.

[Nate Chapin, 2015/04/30 22:26:54]

LoFi images would be replaced with the real image one-at-a-time, right?
ResourceFetcher already has a setting to auto load images, I wonder if we could
modify that to handle this use case.

[megjablon, 2015/04/30 22:35:50]

Yes, we want to only replace one real image at a time. What does auto loading an
image do?

         if (isHTMLPictureElement(element()->parentNode()) || !element()->fastGetAttribute(HTMLNames::srcsetAttr).isNull())
             resourceRequest.setRequestContext(WebURLRequest::RequestContextImageSet);
         FetchRequest request(resourceRequest, element()->localName(), resourceLoaderOptions);
         configureRequest(request, bypassBehavior, *m_element, document.clientHintsPreferences());
 
         // Prevent the immediate creation of a ResourceLoader (and therefore a network
         // request) for ImageDocument loads. In this case, the image contents have already
         // been requested as a main resource and ImageDocumentParser will take care of
         // funneling the main resource bytes into the ImageResource.
         if (m_loadingImageDocument) {
@@ skipping 55 matching lines @@
     }
 
     if (LayoutImageResource* imageResource = layoutImageResource())
         imageResource->resetAnimation();
 
     // Only consider updating the protection ref-count of the Element immediately before returning
     // from this function as doing so might result in the destruction of this ImageLoader.
     updatedHasPendingEvent();
 }
 
-void ImageLoader::updateFromElement(UpdateFromElementBehavior updateBehavior)
+void ImageLoader::updateFromElement(UpdateFromElementBehavior updateBehavior, bool bypassCache)
 {
     AtomicString imageSourceURL = m_element->imageSourceURL();
     m_suppressErrorEvents = (updateBehavior == UpdateSizeChanged);
 
     if (updateBehavior == UpdateIgnorePreviousError)
         clearFailedLoadURL();
 
     if (!m_failedLoadURL.isEmpty() && imageSourceURL == m_failedLoadURL)
         return;
 
     // If we have a pending task, we have to clear it -- either we're
     // now loading immediately, or we need to reset the task's state.
     if (m_pendingTask) {
         m_pendingTask->clearLoader();
         m_pendingTask.clear();
     }
 
     KURL url = imageSourceToKURL(imageSourceURL);
     if (shouldLoadImmediately(url)) {
-        doUpdateFromElement(DoNotBypassMainWorldCSP, updateBehavior);
+        doUpdateFromElement(DoNotBypassMainWorldCSP, updateBehavior, bypassCache);
         return;
     }
     // Allow the idiom "img.src=''; img.src='.." to clear down the image before
     // an asynchronous load completes.
     if (imageSourceURL.isEmpty()) {
         ImageResource* image = m_image.get();
         if (image)
             image->removeClient(this);
         m_image = nullptr;
     }
@@ skipping 238 matching lines @@
 #endif
 }
 
 #if ENABLE(OILPAN)
 ImageLoader::ImageLoaderClientRemover::~ImageLoaderClientRemover()
 {
     m_loader.willRemoveClient(m_client);
 }
 #endif
 }