Supply default icon to extension icon image.

chrome/browser/extensions/extension_icon_image.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_EXTENSION_ICON_IMAGE_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_ICON_IMAGE_H_
 
 #include <map>
 #include <string>
 
 #include "base/basictypes.h"
+#include "base/memory/weak_ptr.h"
 #include "chrome/browser/extensions/image_loading_tracker.h"
 #include "chrome/common/extensions/extension_icon_set.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "ui/gfx/image/image_skia.h"
 
 namespace extensions {
 class Extension;
 }
 
 namespace gfx {
 class Size;
 }
 
 namespace extensions {
 
 // A class that provides an ImageSkia for UI code to use. It handles extension
 // icon resource loading, screen scale factor change etc. UI code that uses
 // extension icon should host this class and be its observer. ExtensionIconImage
 // 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 image representations from the default icon
+// supplied in the constructor. If no default icon is supplied, UI code must
+// make sure null ImageSkiaReps are handled well.

[pkotwicz, 2012/08/22 23:17:55]

An idea: Can we have a default 'default icon' which is completely transparent
but non null?
None of the ImageSkiaSources handle null ImageSkiaReps and I don't think that
they each should have handling to do so (to make writing a new ImageSkiaSource
simple).

[tbarzic, 2012/08/22 23:46:08]

Yeah, I had the same idea (just about to upload the new version).

 class IconImage : public ImageLoadingTracker::Observer,
                   public content::NotificationObserver {
  public:
   class Observer {
    public:
     // Invoked when a new image rep for an additional scale factor
     // is loaded and added to |image|.
     virtual void OnExtensionIconImageChanged(IconImage* image) = 0;
 
-    // Invoked when the icon image couldn't be loaded.
+    // Invoked when the icon image couldn't be loaded. This will always be
+    // called asynchronously.
     virtual void OnIconImageLoadFailed(IconImage* image,
                                        ui::ScaleFactor scale_factor) = 0;
 
    protected:
     virtual ~Observer() {}
   };
 
   IconImage(const Extension* extension,
             const ExtensionIconSet& icon_set,
             int resource_size_in_dip,
+            const gfx::ImageSkia& default_icon,
             Observer* observer);
   virtual ~IconImage();
 
   const gfx::ImageSkia& image_skia() const { return image_skia_; }
 
  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,
                              const std::string& extension_id,
                              int index) OVERRIDE;
 
   // content::NotificationObserver overrides:
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  void NotifyFail(ui::ScaleFactor scale_factor);
+
   const Extension* extension_;
   const ExtensionIconSet& icon_set_;
   const int resource_size_in_dip_;
   const gfx::Size desired_size_in_dip_;
 
   Observer* observer_;
 
   Source* source_;  // Owned by ImageSkia storage.
   gfx::ImageSkia image_skia_;
 
   ImageLoadingTracker tracker_;
   content::NotificationRegistrar registrar_;
 
+  base::WeakPtrFactory<IconImage> weak_ptr_factory_;
+
   LoadMap load_map_;
 
   DISALLOW_COPY_AND_ASSIGN(IconImage);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_ICON_IMAGE_H_