Linux: implement Page Actions support.

chrome/browser/image_loading_tracker.h

+// Copyright (c) 2009 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_IMAGE_LOADING_TRACKER_H_
+#define CHROME_BROWSER_IMAGE_LOADING_TRACKER_H_
+
+#include "base/ref_counted.h"
+
+class FilePath;
+class SkBitmap;
+
+// The views need to load their icons asynchronously but might be deleted before
+// the images have loaded. This class stays alive while the request is in
+// progress (manages its own lifetime) and keeps track of whether the view still
+// cares about the icon loading.
+class ImageLoadingTracker
+  : public base::RefCountedThreadSafe<ImageLoadingTracker> {
+ public:
+  class Observer {
+   public:
+    // Will be called when the image with the given index has loaded.
+    // The |image| is owned by the tracker, so the observer should make a copy
+    // if they need to access it after this call.
+    virtual void OnImageLoaded(SkBitmap* image, size_t index) = 0;
+  };
+
+  ImageLoadingTracker(Observer* observer, size_t image_count)
+    : observer_(observer), image_count_(image_count), posted_count_(0) {
+    AddRef();  // We hold on to a reference to ourself to make sure we don't
+               // get deleted until we get a response from image loading (see
+               // ImageLoadingDone).
+  }
+  ~ImageLoadingTracker() {}
+
+  // If there are remaining images to be loaded, the observing object should
+  // call this method on its destruction, so that the tracker will not attempt
+  // to make any more callbacks to it.
+  void StopTrackingImageLoad() {
+    observer_ = NULL;
+  }
+
+  // Specify path of image to load.  This method must be called a number of
+  // times equal to the |image_count| arugment to the constructor.  Calling it
+  // any more or less than that is an error.
+  void PostLoadImageTask(FilePath path);
+
+ private:
+  class LoadImageTask;
+
+  // When an image has finished loaded and scaled on the file thread, it is
+  // posted back to this method on the original thread.  This method then calls
+  // the observer's OnImageLoaded and deletes the ImageLoadingTracker if it was
+  // the last image in the list.
+  // |image| may be null if the file failed to decode.
+  void OnImageLoaded(SkBitmap* image, size_t index);
+
+  // The view that is waiting for the image to load.
+  Observer* observer_;
+
+  // The number of images this ImageTracker should keep track of.  This is
+  // decremented as each image finishes loading, and the tracker will delete
+  // itself when it reaches zero.
+  size_t image_count_;
+
+  // The number of tasks that have been posted so far.
+  size_t posted_count_;
+
+  DISALLOW_COPY_AND_ASSIGN(ImageLoadingTracker);
+};
+
+#endif  // CHROME_BROWSER_IMAGE_LOADING_TRACKER_H_