Fix double delete of ImageLoadingTracker in BrowserActionButton.

chrome/browser/gtk/browser_actions_toolbar_gtk.cc

 // 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.
 
 #include "chrome/browser/gtk/browser_actions_toolbar_gtk.h"
 
 #include <gtk/gtk.h>
 #include <vector>
 
 #include "app/gfx/canvas_paint.h"
@@ skipping 87 matching lines @@
     else if (type == NotificationType::BROWSER_THEME_CHANGED)
       OnThemeChanged();
     else
       NOTREACHED();
   }
 
   // ImageLoadingTracker::Observer implementation.
   void OnImageLoaded(SkBitmap* image, size_t index) {
     if (image)
       default_icon_ = gfx::GdkPixbufFromSkBitmap(image);
+    tracker_ = NULL;  // The tracker object will delete itself when we return.
     UpdateState();
   }
 
   // Updates the button based on the latest state from the associated
   // browser action.
   void UpdateState() {
     int tab_id = toolbar_->GetCurrentTabId();
     if (tab_id < 0)
       return;
 
@@ skipping 158 matching lines @@
   if (extension_button_map_.erase(extension->id()))
     UpdateVisibility();
 }
 
 void BrowserActionsToolbarGtk::UpdateVisibility() {
   if (button_count() == 0)
     gtk_widget_hide(widget());
   else
     gtk_widget_show(widget());
 }