downloads: break downloads.js into more classes/files.

chrome/browser/ui/webui/downloads_dom_handler.h

Index: chrome/browser/ui/webui/downloads_dom_handler.h
diff --git a/chrome/browser/ui/webui/downloads_dom_handler.h b/chrome/browser/ui/webui/downloads_dom_handler.h
index 85fdbd8a792d3514b631a9988c94df9690134c81..f57a861a89915ab971b5d2d0107da320b8650e1d 100644
--- a/chrome/browser/ui/webui/downloads_dom_handler.h
+++ b/chrome/browser/ui/webui/downloads_dom_handler.h
@@ -96,8 +96,8 @@ class DownloadsDOMHandler : public content::WebUIMessageHandler,
   // depend on WebUI. The other methods that depend on WebUI are
   // RegisterMessages() and HandleDrag().
   virtual content::WebContents* GetWebUIWebContents();
-  virtual void CallDownloadsList(const base::ListValue& downloads);
-  virtual void CallDownloadUpdated(const base::ListValue& download);
+  virtual void CallUpdateAll(const base::ListValue& list);
+  virtual void CallUpdateItem(const base::DictionaryValue& item);
 
   // Schedules a call to SendCurrentDownloads() in the next message loop
   // iteration. Protected rather than private for use in tests.
@@ -158,6 +158,9 @@ class DownloadsDOMHandler : public content::WebUIMessageHandler,
   // Whether a call to SendCurrentDownloads() is currently scheduled.
   bool update_scheduled_;
 
+  // IDs of new downloads that the page doesn't know about yet.
+  std::set<uint32> new_downloads_;
+
   base::WeakPtrFactory<DownloadsDOMHandler> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadsDOMHandler);