linux_aura: Fix tab dragging performance.

ui/views/widget/desktop_root_window_host_linux.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_root_window_host_linux.h"
 
 #include <X11/extensions/XInput2.h>
 #include <X11/Xatom.h>
 #include <X11/Xutil.h>
 
@@ skipping 891 matching lines @@
         // }
         case ui::ET_MOUSE_MOVED:
         case ui::ET_MOUSE_DRAGGED:
         case ui::ET_MOUSE_PRESSED:
         case ui::ET_MOUSE_RELEASED:
         case ui::ET_MOUSE_ENTERED:
         case ui::ET_MOUSE_EXITED: {
           if (type == ui::ET_MOUSE_MOVED || type == ui::ET_MOUSE_DRAGGED) {
             // If this is a motion event, we want to coalesce all pending motion
             // events that are at the top of the queue.
-            // num_coalesced = CoalescePendingMotionEvents(xev, &last_event);
-            // if (num_coalesced > 0)
-            //   xev = &last_event;
+            num_coalesced = ui::CoalescePendingMotionEvents(xev, &last_event);
+            if (num_coalesced > 0)
+              xev = &last_event;
           } else if (type == ui::ET_MOUSE_PRESSED) {
             XIDeviceEvent* xievent =
                 static_cast<XIDeviceEvent*>(xev->xcookie.data);
             int button = xievent->detail;
             if (button == kBackMouseButton || button == kForwardMouseButton) {
               aura::client::UserActionClient* gesture_client =
                   aura::client::GetUserActionClient(
                       root_window_host_delegate_->AsRootWindow());
               if (gesture_client) {
                 bool reverse_direction =
@@ skipping 124 matching lines @@
 DesktopRootWindowHost* DesktopRootWindowHost::Create(
     internal::NativeWidgetDelegate* native_widget_delegate,
     DesktopNativeWidgetAura* desktop_native_widget_aura,
     const gfx::Rect& initial_bounds) {
   return new DesktopRootWindowHostLinux(native_widget_delegate,
                                         desktop_native_widget_aura,
                                         initial_bounds);
 }
 
 }  // namespace views