Supply default icon to extension icon image.

chrome/browser/extensions/extension_icon_image.h

Index: chrome/browser/extensions/extension_icon_image.h
diff --git a/chrome/browser/extensions/extension_icon_image.h b/chrome/browser/extensions/extension_icon_image.h
index c2f98526e4224985aa7fdbe983876f76b9af956e..1c2e04870905832bae40e863235fa2d3ccf2d4ed 100644
--- a/chrome/browser/extensions/extension_icon_image.h
+++ b/chrome/browser/extensions/extension_icon_image.h
@@ -31,7 +31,12 @@ namespace extensions {
 // should be outlived by the observer. In painting code, UI code paints with the
 // ImageSkia provided by this class. If required extension icon resource is not
 // present, this class uses ImageLoadingTracker to load it and call on its
-// observer interface when the resource is loaded.
+// observer interface when the resource is loaded. Until the resource is loaded,
+// the UI code will be provided with blank, transparent image representation.
+// UI code can supply default icon whose representations will be added to the
+// icon if icon's own representation for some scale factor cannot be loaded.
+// If default icon is supplied, it is assumed that it contains representations
+// for all the scale factors we need.
 class IconImage : public ImageLoadingTracker::Observer,
                   public content::NotificationObserver {
  public:
@@ -41,10 +46,6 @@ class IconImage : public ImageLoadingTracker::Observer,
     // is loaded and added to |image|.
     virtual void OnExtensionIconImageChanged(IconImage* image) = 0;
 
-    // Invoked when the icon image couldn't be loaded.
-    virtual void OnIconImageLoadFailed(IconImage* image,
-                                       ui::ScaleFactor scale_factor) = 0;
-
    protected:
     virtual ~Observer() {}
   };
@@ -52,6 +53,7 @@ class IconImage : public ImageLoadingTracker::Observer,
   IconImage(const Extension* extension,
             const ExtensionIconSet& icon_set,
             int resource_size_in_dip,
+            const gfx::ImageSkia& default_icon,
             Observer* observer);
   virtual ~IconImage();
 
@@ -60,10 +62,15 @@ class IconImage : public ImageLoadingTracker::Observer,
  private:
   class Source;
 
-  typedef std::map<int, ui::ScaleFactor> LoadMap;
+  struct LoadRequest {
+    ui::ScaleFactor scale_factor;
+    bool is_async;
+  };
+
+  typedef std::map<int, LoadRequest> LoadMap;
 
   // Loads bitmap for additional scale factor.
-  void LoadImageForScaleFactor(ui::ScaleFactor scale_factor);
+  gfx::ImageSkiaRep LoadImageForScaleFactor(ui::ScaleFactor scale_factor);
 
   // ImageLoadingTracker::Observer overrides:
   virtual void OnImageLoaded(const gfx::Image& image,
@@ -84,6 +91,9 @@ class IconImage : public ImageLoadingTracker::Observer,
 
   Source* source_;  // Owned by ImageSkia storage.
   gfx::ImageSkia image_skia_;
+  // The icon with whose representation |image_skia_| should be updated if
+  // its own representation load fails.
+  gfx::ImageSkia default_icon_;
 
   ImageLoadingTracker tracker_;
   content::NotificationRegistrar registrar_;