Add Blink support for showing image placeholders using range requests.

third_party/WebKit/Source/core/fetch/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.
@@ skipping 47 matching lines @@
  public:
   using ClientType = ResourceClient;
 
   static ImageResource* fetch(FetchRequest&, ResourceFetcher*);
 
   static ImageResource* create(blink::Image* image) {
     return new ImageResource(image, ResourceLoaderOptions());
   }
 
   static ImageResource* create(const ResourceRequest& request) {
-    return new ImageResource(request, ResourceLoaderOptions());
+    return new ImageResource(request, ResourceLoaderOptions(), false);
   }
 
   ~ImageResource() override;
 
   blink::Image*
   getImage();  // Returns the nullImage() if the image is not available yet.
   bool hasImage() const { return m_image.get(); }
 
   static std::pair<blink::Image*, float> brokenImage(
       float deviceScaleFactor);  // Returns an image and the image's resolution
@@ skipping 22 matching lines @@
   // natural size of the image by the zoom.
   LayoutSize imageSize(
       RespectImageOrientationEnum shouldRespectImageOrientation,
       float multiplier,
       SizeType = IntrinsicSize);
 
   bool isAccessAllowed(SecurityOrigin*);
 
   void updateImageAnimationPolicy();
 
-  // If this ImageResource has the Lo-Fi response headers, reload it with the
-  // Lo-Fi state set to off and bypassing the cache.
-  void reloadIfLoFi(ResourceFetcher*);
+  // If this ImageResource has the Lo-Fi response headers or is a placeholder,
+  // reload the full original image with the Lo-Fi state set to off and
+  // optionally bypassing the cache.
+  void reloadIfLoFi(ResourceFetcher*, bool bypassCache = true);

[Stephen Chennney, 2016/10/17 18:09:17]

Rename this to reloadIfLoFiOrPlaceholder.

[sclittle, 2016/10/18 00:54:11]

Done.

 
   void didAddClient(ResourceClient*) override;
 
   void addObserver(ImageResourceObserver*);
   void removeObserver(ImageResourceObserver*);
 
   ResourcePriority priorityFromObservers() override;
 
   void allClientsAndObserversRemoved() override;
 
@@ skipping 14 matching lines @@
   void didDraw(const blink::Image*) override;
 
   bool shouldPauseAnimation(const blink::Image*) override;
   void animationAdvanced(const blink::Image*) override;
   void changedInRect(const blink::Image*, const IntRect&) override;
 
   // MultipartImageResourceParser::Client
   void onePartInMultipartReceived(const ResourceResponse&) final;
   void multipartDataReceived(const char*, size_t) final;
 
+  bool isPlaceholder() const { return m_isPlaceholder; }
+  bool shouldReloadBrokenPlaceholder() const {
+    return m_isPlaceholder && willPaintBrokenImage();
+  }
+
   DECLARE_VIRTUAL_TRACE();
 
  private:
   explicit ImageResource(blink::Image*, const ResourceLoaderOptions&);
 
   enum class MultipartParsingState : uint8_t {
     WaitingForFirstPart,
     ParsingFirstPart,
     FinishedParsingFirstPart,
   };
 
-  class ImageResourceFactory : public ResourceFactory {
-   public:
-    ImageResourceFactory() : ResourceFactory(Resource::Image) {}
+  class ImageResourceFactory;
 
-    Resource* create(const ResourceRequest& request,
-                     const ResourceLoaderOptions& options,
-                     const String&) const override {
-      return new ImageResource(request, options);
-    }
-  };
-  ImageResource(const ResourceRequest&, const ResourceLoaderOptions&);
+  ImageResource(const ResourceRequest&,
+                const ResourceLoaderOptions&,
+                bool isPlaceholder);
 
   bool hasClientsOrObservers() const override {
     return Resource::hasClientsOrObservers() || !m_observers.isEmpty() ||
            !m_finishedObservers.isEmpty();
   }
   void clear();
 
   void createImage();
   void updateImage(bool allDataReceived);
   void updateImageAndClearBuffer();
@@ skipping 18 matching lines @@
   RefPtr<blink::Image> m_image;
   MultipartParsingState m_multipartParsingState =
       MultipartParsingState::WaitingForFirstPart;
   bool m_hasDevicePixelRatioHeaderValue;
   HashCountedSet<ImageResourceObserver*> m_observers;
   HashCountedSet<ImageResourceObserver*> m_finishedObservers;
 
   // 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;
 };
 
 DEFINE_RESOURCE_TYPE_CASTS(Image);
 
 }  // namespace blink
 
 #endif