Implement chrome.experimental.downloads.onChanged

chrome/browser/extensions/extension_downloads_api.h

 // Copyright (c) 2011 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_DOWNLOADS_API_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_DOWNLOADS_API_H_
 #pragma once
 
 #include <map>
 #include <set>
 #include <string>
 
 #include "base/file_path.h"
 #include "base/memory/singleton.h"
+#include "base/stl_util.h"
 #include "base/string16.h"
 #include "chrome/browser/extensions/extension_function.h"
 #include "content/browser/download/download_item.h"
 #include "content/browser/download/download_manager.h"
 
 namespace base {
 class DictionaryValue;
 }
 class ResourceDispatcherHost;
 class TabContents;
@@ skipping 223 matching lines @@
   DECLARE_EXTENSION_FUNCTION_NAME("experimental.downloads.drag");
 
  protected:
   virtual bool ParseArgs() OVERRIDE;
   virtual void RunInternal() OVERRIDE;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DownloadsDragFunction);
 };
 
+// Observes a single DownloadManager and dispatches onCreated and onErased
+// events.
 class ExtensionDownloadsEventRouter : public DownloadManager::Observer {
  public:
   explicit ExtensionDownloadsEventRouter(Profile* profile);
   virtual ~ExtensionDownloadsEventRouter();
 
   virtual void ModelChanged() OVERRIDE;
   virtual void ManagerGoingDown() OVERRIDE;
 
  private:
-  void DispatchEvent(const char* event_name, base::Value* json_arg);
+  // Observes a single DownloadItem and dispatches onChanged events.

[Randy Smith (Not in Mondays), 2011/10/12 18:46:30]

Might want a comment here as to why it's not a mix-in on the base class.  I'm
almost tempted to suggest you do that instead; I think fewer classes is better
than more, and it'd save you some of the inter-class interaction at the cost of
having to keep a more complex datastructure of the last state seen.

[benjhayden, 2011/10/13 16:30:29]

Done.

+  class ItemObserver : public DownloadItem::Observer {
+   public:
+    typedef base::Callback<void(base::Value*)> EventDispatcher;
+    ItemObserver(const EventDispatcher& dispatcher, DownloadItem* item);
+    virtual ~ItemObserver();
+
+    virtual void OnDownloadUpdated(DownloadItem* download);
+    virtual void OnDownloadOpened(DownloadItem* download);
+
+   private:
+    EventDispatcher dispatcher_;
+    DownloadItem* item_;
+    scoped_ptr<base::DictionaryValue> json_;
+
+    DISALLOW_COPY_AND_ASSIGN(ItemObserver);
+  };
+
   typedef base::hash_map<int, DownloadItem*> ItemMap;
   typedef std::set<int> DownloadIdSet;
+  typedef base::hash_map<int, ItemObserver*> ItemObserverMap;
+
+  void DispatchEvent(const char* event_name, base::Value* json_arg);
 
   Profile* profile_;
   DownloadManager* manager_;
   DownloadIdSet downloads_;
+  ItemObserverMap item_observers_;
+  STLValueDeleter<ItemObserverMap> delete_item_observers_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionDownloadsEventRouter);
 };
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_DOWNLOADS_API_H_