Phase II Step 3: Reload LoFi/placeholder images via new ImageResource

third_party/WebKit/Source/core/loader/resource/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 23 matching lines @@
 #include "platform/SharedBuffer.h"
 #include "platform/instrumentation/tracing/TraceEvent.h"
 #include "platform/loader/fetch/MemoryCache.h"
 #include "platform/loader/fetch/ResourceClient.h"
 #include "platform/loader/fetch/ResourceFetcher.h"
 #include "platform/loader/fetch/ResourceLoader.h"
 #include "platform/loader/fetch/ResourceLoadingLog.h"
 #include "platform/network/HTTPParsers.h"
 #include "platform/weborigin/SecurityViolationReportingPolicy.h"
 #include "public/platform/Platform.h"
+#include "public/platform/WebCachePolicy.h"
 #include "v8/include/v8.h"
 #include "wtf/CurrentTime.h"
 #include "wtf/StdLibExtras.h"
 
 namespace blink {
 namespace {
 // The amount of time to wait before informing the clients that the image has
 // been updated (in seconds). This effectively throttles invalidations that
 // result from new data arriving for this image.
 constexpr double kFlushDelaySeconds = 1.;
 }  // namespace
 
 class ImageResource::ImageResourceInfoImpl final
     : public GarbageCollectedFinalized<ImageResourceInfoImpl>,
       public ImageResourceInfo {
   USING_GARBAGE_COLLECTED_MIXIN(ImageResourceInfoImpl);
 
  public:
   ImageResourceInfoImpl(ImageResource* resource) : m_resource(resource) {
     DCHECK(m_resource);
   }
   DEFINE_INLINE_VIRTUAL_TRACE() {
     visitor->trace(m_resource);
     ImageResourceInfo::trace(visitor);
   }
 
  private:
   const KURL& url() const override { return m_resource->url(); }
-  bool isSchedulingReload() const override {
-    return m_resource->m_isSchedulingReload;
-  }
   bool hasDevicePixelRatioHeaderValue() const override {
     return m_resource->m_hasDevicePixelRatioHeaderValue;
   }
   float devicePixelRatioHeaderValue() const override {
     return m_resource->m_devicePixelRatioHeaderValue;
   }
   const ResourceResponse& response() const override {
     return m_resource->response();
   }
   ResourceStatus getStatus() const override { return m_resource->getStatus(); }
   bool shouldShowPlaceholder() const override {
     return m_resource->shouldShowPlaceholder();
   }
   bool isCacheValidator() const override {
     return m_resource->isCacheValidator();
   }
-  bool schedulingReloadOrShouldReloadBrokenPlaceholder() const override {
-    return m_resource->m_isSchedulingReload ||
-           m_resource->shouldReloadBrokenPlaceholder();
-  }
   bool isAccessAllowed(
       SecurityOrigin* securityOrigin,
       DoesCurrentFrameHaveSingleSecurityOrigin
           doesCurrentFrameHasSingleSecurityOrigin) const override {
     return m_resource->isAccessAllowed(securityOrigin,
                                        doesCurrentFrameHasSingleSecurityOrigin);
   }
   bool hasCacheControlNoStoreHeader() const override {
     return m_resource->hasCacheControlNoStoreHeader();
   }
@@ skipping 63 matching lines @@
         fetcher->context().sendImagePing(requestURL);
     }
     return nullptr;
   }
 
   return toImageResource(
       fetcher->requestResource(request, ImageResourceFactory(request)));
 }
 
 bool ImageResource::canReuse(const FetchRequest& request) const {
+  if (!getContent())
+    return false;
+
   // If the image is a placeholder, but this fetch doesn't allow a
   // placeholder, then do not reuse this resource.
   if (request.placeholderImageRequestType() != FetchRequest::AllowPlaceholder &&
       m_placeholderOption != PlaceholderOption::DoNotReloadPlaceholder)
     return false;
+
   return true;
 }
 
 ImageResource* ImageResource::create(const ResourceRequest& request) {
   return new ImageResource(request, ResourceLoaderOptions(),
                            ImageResourceContent::create(), false);
 }
 
 ImageResource::ImageResource(const ResourceRequest& resourceRequest,
                              const ResourceLoaderOptions& options,
                              ImageResourceContent* content,
                              bool isPlaceholder)
     : Resource(resourceRequest, Image, options),
       m_content(content),
       m_devicePixelRatioHeaderValue(1.0),
       m_hasDevicePixelRatioHeaderValue(false),
-      m_isSchedulingReload(false),
       m_placeholderOption(
           isPlaceholder ? PlaceholderOption::ShowAndReloadPlaceholderAlways
                         : PlaceholderOption::DoNotReloadPlaceholder),
       m_flushTimer(this, &ImageResource::flushImageIfNeeded) {
   DCHECK(getContent());
   RESOURCE_LOADING_DVLOG(1) << "new ImageResource(ResourceRequest) " << this;
   getContent()->setImageResourceInfo(new ImageResourceInfoImpl(this));
 }
 
 ImageResource::~ImageResource() {
   RESOURCE_LOADING_DVLOG(1) << "~ImageResource " << this;
 }
 
 DEFINE_TRACE(ImageResource) {
   visitor->trace(m_multipartParser);
   visitor->trace(m_content);
   Resource::trace(visitor);
   MultipartImageResourceParser::Client::trace(visitor);
 }
 
-void ImageResource::checkNotify() {
-  // Don't notify clients of completion if this ImageResource is
-  // about to be reloaded.
-  if (m_isSchedulingReload || shouldReloadBrokenPlaceholder())
-    return;
-
-  Resource::checkNotify();
-}
-
 bool ImageResource::hasClientsOrObservers() const {
-  return Resource::hasClientsOrObservers() || getContent()->hasObservers();
+  return Resource::hasClientsOrObservers() ||
+         (getContent() && getContent()->hasObservers());
 }
 
 void ImageResource::didAddClient(ResourceClient* client) {
   DCHECK((m_multipartParser && isLoading()) || !data() ||
-         getContent()->hasImage());
-
-  // Don't notify observers and clients of completion if this ImageResource is
-  // about to be reloaded.
-  if (m_isSchedulingReload || shouldReloadBrokenPlaceholder())
-    return;
-
+         (getContent() && getContent()->hasImage()));
   Resource::didAddClient(client);
 }
 
 void ImageResource::destroyDecodedDataForFailedRevalidation() {
   // Clears the image, as we must create a new image for the failed
   // revalidation response.
   updateImage(nullptr, ImageResourceContent::ClearAndUpdateImage, false);
   setDecodedSize(0);
 }
 
 void ImageResource::destroyDecodedDataIfPossible() {
+  if (!getContent())
+    return;
   getContent()->destroyDecodedData();
   if (getContent()->hasImage() && !isPreloaded() &&
       getContent()->isRefetchableDataFromDiskCache()) {
     UMA_HISTOGRAM_MEMORY_KB("Memory.Renderer.EstimatedDroppableEncodedSize",
                             encodedSize() / 1024);
   }
 }
 
 void ImageResource::allClientsAndObserversRemoved() {
-  CHECK(!getContent()->hasImage() || !errorOccurred());
+  CHECK(!getContent() || !getContent()->hasImage() || !errorOccurred());
   // If possible, delay the resetting until back at the event loop. Doing so

[yhirano, 2017/03/17 13:09:35]

This comment should be inside of the outer if statement.

   // after a conservative GC prevents resetAnimation() from upsetting ongoing
   // animation updates (crbug.com/613709)
-  if (!ThreadHeap::willObjectBeLazilySwept(this)) {
-    Platform::current()->currentThread()->getWebTaskRunner()->postTask(
-        BLINK_FROM_HERE, WTF::bind(&ImageResourceContent::doResetAnimation,
-                                   wrapWeakPersistent(getContent())));
-  } else {
-    getContent()->doResetAnimation();
+  if (getContent()) {
+    if (!ThreadHeap::willObjectBeLazilySwept(this)) {
+      Platform::current()->currentThread()->getWebTaskRunner()->postTask(
+          BLINK_FROM_HERE, WTF::bind(&ImageResourceContent::doResetAnimation,
+                                     wrapWeakPersistent(getContent())));
+    } else {
+      getContent()->doResetAnimation();
+    }
   }
   if (m_multipartParser)
     m_multipartParser->cancel();
   Resource::allClientsAndObserversRemoved();
 }
 
 PassRefPtr<const SharedBuffer> ImageResource::resourceBuffer() const {
   if (data())

[kouhei (in TOK), 2017/03/15 10:25:28]

Is this when we tried to access ::resourceBuffer while image is being loaded?

[hiroshige, 2017/03/15 19:03:31]

Yes.

(Probably we check getContent() first for consistency; anyway I expect data() is
null when getContent() is null)

     return data();
+  if (!getContent())
+    return nullptr;
   return getContent()->resourceBuffer();
 }
 
 void ImageResource::appendData(const char* data, size_t length) {
   v8::Isolate::GetCurrent()->AdjustAmountOfExternalAllocatedMemory(length);
   if (m_multipartParser) {
     m_multipartParser->appendData(data, length);
   } else {
     Resource::appendData(data, length);
 
+    if (!getContent())
+      return;
+
     // Update the image immediately if needed.
     if (getContent()->shouldUpdateImageImmediately()) {
       updateImage(this->data(), ImageResourceContent::UpdateImage, false);
       return;
     }
 
     // For other cases, only update at |kFlushDelaySeconds| intervals. This
     // throttles how frequently we update |m_image| and how frequently we
     // inform the clients which causes an invalidation of this image. In other
     // words, we only invalidate this image every |kFlushDelaySeconds| seconds
@@ skipping 22 matching lines @@
 }
 
 void ImageResource::decodeError(bool allDataReceived) {
   size_t size = encodedSize();
 
   clearData();
   setEncodedSize(0);
   if (!errorOccurred())
     setStatus(ResourceStatus::DecodeError);
 
+  // Tries to reload here to avoid imageNotifyFinished()
+  // notification in the case of decode error.
+  if (loader())
+    loader()->reloadIfLoFiOrPlaceholderImage(this);
+
   // Finishes loading if needed, and notifies observers.
   if (!allDataReceived && loader()) {
     // Observers are notified via ImageResource::finish().
     // TODO(hiroshige): Do not call didFinishLoading() directly.
     loader()->didFinishLoading(monotonicallyIncreasingTime(), size, size);
-  } else {
+  } else if (getContent()) {
     auto result = getContent()->updateImage(
         nullptr, ImageResourceContent::ClearImageAndNotifyObservers,
         allDataReceived);
     DCHECK_EQ(result, ImageResourceContent::UpdateImageResult::NoDecodeError);
   }
 
   memoryCache()->remove(this);
 }
 
 void ImageResource::updateImageAndClearBuffer() {
@@ skipping 102 matching lines @@
       return errorOccurred();
     case PlaceholderOption::ReloadPlaceholderOnDecodeError:
       return getStatus() == ResourceStatus::DecodeError;
     case PlaceholderOption::DoNotReloadPlaceholder:
       return false;
   }
   NOTREACHED();
   return false;
 }
 
+void ImageResource::detachContent() {
+  bool hasObservers = getContent() && getContent()->hasObservers();

[kouhei (in TOK), 2017/03/15 10:25:28]

Optional: contentHadObservers?

+
+  m_content = nullptr;
+  clearData();
+  memoryCache()->remove(this);
+
+  if (hasObservers)
+    didRemoveClientOrObserver();
+}
+
 static bool isLoFiImage(const ImageResource& resource) {
   if (!(resource.resourceRequest().previewsState() &
         WebURLRequest::ServerLoFiOn)) {
     return false;
   }
   return !resource.isLoaded() ||
          resource.response()
              .httpHeaderField("chrome-proxy-content-transform")
              .contains("empty-image");
 }
 
-void ImageResource::reloadIfLoFiOrPlaceholderImage(
+ImageResource* ImageResource::reloadIfLoFiOrPlaceholderImage(
     ResourceFetcher* fetcher,
     ReloadLoFiOrPlaceholderPolicy policy) {
+  if (!fetcher)

[yhirano, 2017/03/17 13:09:35]

Is passing nullptr valid?

+    return nullptr;
+
   if (policy == kReloadIfNeeded && !shouldReloadBrokenPlaceholder())
-    return;
+    return nullptr;
 
   if (m_placeholderOption == PlaceholderOption::DoNotReloadPlaceholder &&
       !isLoFiImage(*this))
-    return;
+    return nullptr;
 
-  // Prevent clients and observers from being notified of completion while the
-  // reload is being scheduled, so that e.g. canceling an existing load in
-  // progress doesn't cause clients and observers to be notified of completion
-  // prematurely.
-  DCHECK(!m_isSchedulingReload);
-  m_isSchedulingReload = true;
+  ImageResourceContent* content = getContent();
+  if (!content)
+    return nullptr;
 
-  setCachePolicyBypassingCache();
+  // Creates request/options for new ImageResource for reloading.
+  ResourceLoaderOptions reloadingOptions = options();
+  ResourceRequest reloadingRequest = resourceRequest();
+  reloadingRequest.setCachePolicy(WebCachePolicy::BypassingCache);
+  reloadingRequest.setPreviewsState(WebURLRequest::PreviewsNoTransform);
+  if (m_placeholderOption != PlaceholderOption::DoNotReloadPlaceholder)
+    reloadingRequest.clearHTTPHeaderField("range");
 
-  setPreviewsStateNoTransform();
+  // Clear the image before reloading starts to avoid mixing the image from
+  // previous response with the response from the new reloading response.
+  updateImage(nullptr, ImageResourceContent::ClearImageAndNotifyObservers,
+              false);
 
-  if (m_placeholderOption != PlaceholderOption::DoNotReloadPlaceholder)
-    clearRangeRequestHeader();
-  m_placeholderOption = PlaceholderOption::DoNotReloadPlaceholder;
+  detachContent();
+  // |this->getContent()| is nullptr after this point.
 
-  if (isLoading()) {
-    loader()->cancel();
-    // Canceling the loader causes error() to be called, which in turn calls
-    // clear() and notifyObservers(), so there's no need to call these again
-    // here.
-  } else {
-    clearData();
-    setEncodedSize(0);
-    updateImage(nullptr, ImageResourceContent::ClearImageAndNotifyObservers,
-                false);
-  }
+  // TODO(hiroshige): Use ResourceFetcher::requestResource() to unify the
+  // starting points of resource loading into requestResource().
+  // Currently we call ResourceFetcher::startLoad() instead, in order to avoid
+  // re-applying modifications to ResourceRequest in requestResource().
+  ImageResource* reloadingResource =
+      new ImageResource(reloadingRequest, reloadingOptions, content, false);
+  DCHECK(!reloadingResource || content == reloadingResource->getContent());
+  memoryCache()->add(reloadingResource);
+  fetcher->addToDocumentResources(reloadingResource);
+  fetcher->startLoad(reloadingResource);
 
-  setStatus(ResourceStatus::NotStarted);
-
-  DCHECK(m_isSchedulingReload);
-  m_isSchedulingReload = false;
-
-  fetcher->startLoad(this);
+  return reloadingResource;
 }
 
 void ImageResource::onePartInMultipartReceived(
     const ResourceResponse& response) {
   DCHECK(m_multipartParser);
 
   setResponse(response);
   if (m_multipartParsingState == MultipartParsingState::WaitingForFirstPart) {
     // We have nothing to do because we don't have any data.
     m_multipartParsingState = MultipartParsingState::ParsingFirstPart;
@@ skipping 38 matching lines @@
 
 ImageResourceContent* ImageResource::getContent() {
   return m_content;
 }
 
 const ImageResourceContent* ImageResource::getContent() const {
   return m_content;
 }
 
 ResourcePriority ImageResource::priorityFromObservers() {
+  if (!getContent())
+    return ResourcePriority();
   return getContent()->priorityFromObservers();
 }
 
 void ImageResource::updateImage(
     PassRefPtr<SharedBuffer> sharedBuffer,
     ImageResourceContent::UpdateImageOption updateImageOption,
     bool allDataReceived) {
+  if (!getContent())
+    return;
   auto result = getContent()->updateImage(std::move(sharedBuffer),
                                           updateImageOption, allDataReceived);
   if (result == ImageResourceContent::UpdateImageResult::ShouldDecodeError) {
+    // TODO before commit (hiroshige): Update the comment.
     // In case of decode error, we call imageNotifyFinished() iff we don't
     // initiate reloading:
     // [(a): when this is in the middle of loading, or (b): otherwise]
     // 1. The updateImage() call above doesn't call notifyObservers().
     // 2. notifyObservers(ShouldNotifyFinish) is called
     //    (a) via updateImage() called in ImageResource::finish()
     //        called via didFinishLoading() called in decodeError(), or
     //    (b) via updateImage() called in decodeError().
     //    imageNotifyFinished() is called here iff we will not initiate
     //    reloading in Step 3 due to notifyObservers()'s
     //    schedulingReloadOrShouldReloadBrokenPlaceholder() check.
     // 3. reloadIfLoFiOrPlaceholderImage() is called via ResourceFetcher
     //    (a) via didFinishLoading() called in decodeError(), or
     //    (b) after returning ImageResource::updateImage().
     decodeError(allDataReceived);
   }
 }
 
 }  // namespace blink