Fix the bug that closing a tab which owns a fullscreen Flash widget causes crash.

webkit/plugins/ppapi/ppapi_plugin_instance.cc

 // 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.
 
 #include "webkit/plugins/ppapi/ppapi_plugin_instance.h"
 
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop.h"
@@ skipping 242 matching lines @@
   pp_instance_ = ResourceTracker::Get()->AddInstance(this);
 
   memset(&current_print_settings_, 0, sizeof(current_print_settings_));
   DCHECK(delegate);
   module_->InstanceCreated(this);
   delegate_->InstanceCreated(this);
   message_channel_.reset(new MessageChannel(this));
 }
 
 PluginInstance::~PluginInstance() {
+  DCHECK(!fullscreen_container_);
+
   // Free all the plugin objects. This will automatically clear the back-
   // pointer from the NPObject so WebKit can't call into the plugin any more.
   //
   // Swap out the set so we can delete from it (the objects will try to
   // unregister themselves inside the delete call).
   PluginObjectSet plugin_object_copy;
   live_plugin_objects_.swap(plugin_object_copy);
   for (PluginObjectSet::iterator i = plugin_object_copy.begin();
        i != plugin_object_copy.end(); ++i)
     delete *i;
@@ skipping 1443 matching lines @@
   }
   WebKit::WebDocument main_document =
       containing_document.frame()->view()->mainFrame()->document();
 
   return containing_document.securityOrigin().canAccess(
       main_document.securityOrigin());
 }
 
 }  // namespace ppapi
 }  // namespace webkit