linux_aura: Fix tab dragging performance.

ui/views/widget/desktop_root_window_host_linux.cc

Index: ui/views/widget/desktop_root_window_host_linux.cc
diff --git a/ui/views/widget/desktop_root_window_host_linux.cc b/ui/views/widget/desktop_root_window_host_linux.cc
index 25d9846078b04ecd860bdd5f038c7a5f205ba9b6..03729b603194456feaa78a2e7e0b25bb7b5e1ae4 100644
--- a/ui/views/widget/desktop_root_window_host_linux.cc
+++ b/ui/views/widget/desktop_root_window_host_linux.cc
@@ -909,9 +909,9 @@ bool DesktopRootWindowHostLinux::Dispatch(const base::NativeEvent& event) {
           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);