Change ordering of Shell event handlers:

ash/drag_drop/drag_drop_controller.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 "ash/drag_drop/drag_drop_controller.h"
 
 #include "ash/drag_drop/drag_drop_tracker.h"
 #include "ash/drag_drop/drag_image_view.h"
 #include "ash/shell.h"
 #include "ash/wm/coordinate_conversion.h"
@@ skipping 130 matching lines @@
 DragDropController::DragDropController()
     : drag_image_(NULL),
       drag_data_(NULL),
       drag_operation_(0),
       drag_window_(NULL),
       drag_source_window_(NULL),
       should_block_during_drag_drop_(true),
       drag_drop_window_delegate_(new DragDropTrackerDelegate(this)),
       current_drag_event_source_(ui::DragDropTypes::DRAG_EVENT_SOURCE_MOUSE),
       weak_factory_(this) {
-  Shell::GetInstance()->AddPreTargetHandler(this);
+  Shell::GetInstance()->PrependPreTargetHandler(this);
 }
 
 DragDropController::~DragDropController() {
   Shell::GetInstance()->RemovePreTargetHandler(this);
   Cleanup();
   if (cancel_animation_)
     cancel_animation_->End();
   if (drag_image_)
     drag_image_.reset();
 }
@@ skipping 57 matching lines @@
       drag_image_vertical_offset, drag_image_scale, &drag_image_offset_);
   drag_image_->SetBoundsInScreen(drag_image_bounds);
   drag_image_->SetWidgetVisible(true);
 
   drag_window_ = NULL;
 
   // Ends cancel animation if it's in progress.
   if (cancel_animation_)
     cancel_animation_->End();
 
-  // Become the first event handler since we should get first shot at handling
-  // any events during the drag drop session.
-  Shell::GetInstance()->RemovePreTargetHandler(this);
-  Shell::GetInstance()->PrependPreTargetHandler(this);
-
-
 #if !defined(OS_MACOSX)
   if (should_block_during_drag_drop_) {
     base::RunLoop run_loop(aura::Env::GetInstance()->GetDispatcher());
     quit_closure_ = run_loop.QuitClosure();
     base::MessageLoopForUI* loop = base::MessageLoopForUI::current();
     base::MessageLoop::ScopedNestableTaskAllower allow_nested(loop);
     run_loop.Run();
   }
 #endif  // !defined(OS_MACOSX)
 
@@ skipping 320 matching lines @@
     drag_window_->RemoveObserver(this);
   drag_window_ = NULL;
   drag_data_ = NULL;
   // Cleanup can be called again while deleting DragDropTracker, so use Pass
   // instead of reset to avoid double free.
   drag_drop_tracker_.Pass();
 }
 
 }  // namespace internal
 }  // namespace ash