Make the UI an observer of downloads.

chrome/browser/download/download_item_model.cc

Index: chrome/browser/download/download_item_model.cc
diff --git a/chrome/browser/download/download_item_model.cc b/chrome/browser/download/download_item_model.cc
index 192971f32cd06529b35b5cd1833198c690960893..78516f996dd5786d0a3d9b769d76972867df537b 100644
--- a/chrome/browser/download/download_item_model.cc
+++ b/chrome/browser/download/download_item_model.cc
@@ -45,6 +45,11 @@ class DownloadItemModelData : public base::SupportsUserData::Data {
     should_show_in_shelf_ = should_show_in_shelf;
   }
 
+  bool should_notify_ui() const { return should_notify_ui_; }
+  void set_should_notify_ui(bool should_notify_ui) {
+    should_notify_ui_ = should_notify_ui;
+  }
+
  private:
   DownloadItemModelData();
   virtual ~DownloadItemModelData() {}
@@ -54,6 +59,10 @@ class DownloadItemModelData : public base::SupportsUserData::Data {
   // Whether the download should be displayed in the download shelf. True by
   // default.
   bool should_show_in_shelf_;
+
+  // Whether the UI should be notified when the download is ready to be
+  // presented.
+  bool should_notify_ui_;
 };
 
 // static
@@ -78,7 +87,8 @@ DownloadItemModelData* DownloadItemModelData::GetOrCreate(
 }
 
 DownloadItemModelData::DownloadItemModelData()
-    : should_show_in_shelf_(true) {
+    : should_show_in_shelf_(true),
+      should_notify_ui_(false) {
 }
 
 string16 InterruptReasonStatusMessage(int reason) {
@@ -422,6 +432,16 @@ void DownloadItemModel::SetShouldShowInShelf(bool should_show) {
   data->set_should_show_in_shelf(should_show);
 }
 
+bool DownloadItemModel::ShouldNotifyUI() const {
+  const DownloadItemModelData* data = DownloadItemModelData::Get(download_);
+  return data && data->should_notify_ui();
+}
+
+void DownloadItemModel::SetShouldNotifyUI(bool should_notify) {
+  DownloadItemModelData* data = DownloadItemModelData::GetOrCreate(download_);
+  data->set_should_notify_ui(should_notify);
+}
+
 string16 DownloadItemModel::GetProgressSizesString() const {
   string16 size_ratio;
   int64 size = GetCompletedBytes();