[M-37]: Fix dragging tab via mouse when touch is down on ChromeOS

ash/wm/toplevel_window_event_handler.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/wm/toplevel_window_event_handler.h"
 
 #include "ash/shell.h"
 #include "ash/wm/resize_shadow_controller.h"
 #include "ash/wm/window_resizer.h"
 #include "ash/wm/window_state.h"
@@ skipping 476 matching lines @@
     CompleteDrag(DRAG_COMPLETE);
   }
 }
 
 void ToplevelWindowEventHandler::HandleMouseReleased(
     aura::Window* target,
     ui::MouseEvent* event) {
   if (event->phase() != ui::EP_PRETARGET)
     return;
 
-  CompleteDrag(event->type() == ui::ET_MOUSE_RELEASED ?
-                   DRAG_COMPLETE : DRAG_REVERT);
+  if (window_resizer_) {
+    CompleteDrag(event->type() == ui::ET_MOUSE_RELEASED ?
+                     DRAG_COMPLETE : DRAG_REVERT);
+  }
+
   // Completing the drag may result in hiding the window. If this happens
   // mark the event as handled so no other handlers/observers act upon the
   // event. They should see the event on a hidden window, to determine targets
   // of destructive actions such as hiding. They should not act upon them.
   if (window_resizer_ &&
       event->type() == ui::ET_MOUSE_CAPTURE_CHANGED &&
       !target->IsVisible()) {
     event->SetHandled();
   }
 }
@@ skipping 100 matching lines @@
 
 void ToplevelWindowEventHandler::ResizerWindowDestroyed() {
   // We explicitly don't invoke RevertDrag() since that may do things to window.
   // Instead we destroy the resizer.
   window_resizer_.reset();
 
   CompleteDrag(DRAG_REVERT);
 }
 
 }  // namespace ash