Replace "nested message loop" with "nested run loop" in comments.

ui/aura/mus/drag_drop_controller_mus.cc

 // Copyright 2016 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/aura/mus/drag_drop_controller_mus.h"
 
 #include <map>
 #include <string>
 #include <vector>
 
@@ skipping 32 matching lines @@
   // The change id of the drag. Used to identify the drag on the server.
   uint32_t change_id;
 
   // The result of the drag. This is set on completion and returned to the
   // caller.
   uint32_t completed_action;
 
   // OSExchangeData supplied to StartDragAndDrop().
   const ui::OSExchangeData& drag_data;
 
-  // StartDragDrop() runs a nested message loop. This closure is used to quit
+  // StartDragDrop() runs a nested run loop. This closure is used to quit
   // the run loop when the drag completes.
   base::Closure runloop_quit_closure;
 };
 
 DragDropControllerMus::DragDropControllerMus(
     DragDropControllerHost* drag_drop_controller_host,
     ui::mojom::WindowTree* window_tree)
     : drag_drop_controller_host_(drag_drop_controller_host),
       window_tree_(window_tree) {}
 
@@ skipping 149 matching lines @@
   std::unique_ptr<ui::DropTargetEvent> event =
       base::MakeUnique<ui::DropTargetEvent>(
           current_drag_state_ ? current_drag_state_->drag_data
                               : *(os_exchange_data_.get()),
           location, root_location, effect_bitmask);
   event->set_flags(event_flags);
   return event;
 }
 
 }  // namespace aura