Prevents crash when a menu gets closed during drag

ui/views/widget/desktop_aura/desktop_native_widget_aura.cc

 // Copyright (c) 2012 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 "ui/views/widget/desktop_aura/desktop_native_widget_aura.h"
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/client/cursor_client.h"
@@ skipping 472 matching lines @@
 
   static_cast<aura::client::FocusClient*>(focus_client_.get())->
       FocusWindow(content_window_);
 
   OnHostResized(host());
 
   host_->AddObserver(this);
 
   window_tree_client_.reset(
       new DesktopNativeWidgetAuraWindowTreeClient(host_->window()));
-  drop_helper_.reset(new DropHelper(
-      static_cast<internal::RootView*>(GetWidget()->GetRootView())));
+  drop_helper_.reset(new DropHelper(GetWidget()->GetRootView()));
   aura::client::SetDragDropDelegate(content_window_, this);
 
   tooltip_manager_.reset(new TooltipManagerAura(GetWidget()));
 
   tooltip_controller_.reset(
       new corewm::TooltipController(
           desktop_window_tree_host_->CreateTooltip()));
   aura::client::SetTooltipClient(host_->window(),
                                  tooltip_controller_.get());
   host_->window()->AddPreTargetHandler(tooltip_controller_.get());
@@ skipping 79 matching lines @@
 
 ui::Layer* DesktopNativeWidgetAura::GetLayer() {
   return content_window_ ? content_window_->layer() : NULL;
 }
 
 void DesktopNativeWidgetAura::ReorderNativeViews() {
   window_reorderer_->ReorderChildWindows();
 }
 
 void DesktopNativeWidgetAura::ViewRemoved(View* view) {
+  DCHECK(drop_helper_.get() != NULL);
+  drop_helper_->ResetTargetViewIfEquals(view);

[varkha, 2014/03/31 17:40:52]

This is same as the code in NativeWidgetAura::ViewRemoved and is here for the
same reason.
https://code.google.com/p/chromium/codesearch#chromium/src/ui/views/widget/na...

 }
 
 void DesktopNativeWidgetAura::SetNativeWindowProperty(const char* name,
                                                       void* value) {
   if (content_window_)
     content_window_->SetNativeWindowProperty(name, value);
 }
 
 void* DesktopNativeWidgetAura::GetNativeWindowProperty(const char* name) const {
   return content_window_ ?
@@ skipping 586 matching lines @@
   if (cursor_reference_count_ == 0) {
     // We are the last DesktopNativeWidgetAura instance, and we are responsible
     // for cleaning up |cursor_manager_|.
     delete cursor_manager_;
     native_cursor_manager_ = NULL;
     cursor_manager_ = NULL;
   }
 }
 
 }  // namespace views