linux_aura: Fix tab dragging performance.

ui/base/x/x11_util.h

 // 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.
 
 #ifndef UI_BASE_X_X11_UTIL_H_
 #define UI_BASE_X_X11_UTIL_H_
 
 // This file declares utility functions for X11 (Linux only).
 //
 // These functions do not require the Xlib headers to be included (which is why
@@ skipping 287 matching lines @@
 // the process if called. Use SetX11ErrorHandlers() from x11_util_internal.h
 // to set your own error handlers.
 UI_EXPORT void SetDefaultX11ErrorHandlers();
 
 // Return true if a given window is in full-screen mode.
 UI_EXPORT bool IsX11WindowFullScreen(XID window);
 
 // Return true if event type is MotionNotify.
 UI_EXPORT bool IsMotionEvent(XEvent* event);
 
+// Coalesce all pending motion events (touch or mouse) that are at the top of
+// the queue, and return the number eliminated, storing the last one in
+// |last_event|.
+UI_EXPORT int CoalescePendingMotionEvents(const XEvent* xev,
+                                          XEvent* last_event);
+
 // Returns the mapped button.
 int GetMappedButton(int button);
 
 // Updates button mapping. This is usually called when a MappingNotify event is
 // received.
 UI_EXPORT void UpdateButtonMap();
 
 // Initializes a XEvent that holds XKeyEvent for testing. Note that ui::EF_
 // flags should be passed as |flags|, not the native ones in <X11/X.h>.
 UI_EXPORT void InitXKeyEventForTesting(EventType type,
@@ skipping 53 matching lines @@
  private:
   ::Cursor cursor_;
   Display* display_;
 
   DISALLOW_COPY_AND_ASSIGN(XScopedCursor);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_X_X11_UTIL_H_