Add PlatformWindow/Event related code for Ozone X11.

ui/events/x/events_x_utils.h

 // Copyright (c) 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.
 
 #ifndef UI_EVENTS_X_EVENTS_X_UTILS_H_
 #define UI_EVENTS_X_EVENTS_X_UTILS_H_
 
 #include <stdint.h>
 
 #include "base/time/time.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/x/events_x_export.h"
 #include "ui/gfx/geometry/point.h"
+#include "ui/gfx/x/x11_types.h"
 
 typedef union _XEvent XEvent;
 
 namespace ui {
 
-// Get the EventType from a XEvent.
+// Gets the XID of XWindow from a XEvent.
+EVENTS_X_EXPORT XID XWindowFromXEvent(const XEvent& xev);
+
+// Gets the EventType from a XEvent.
 EVENTS_X_EXPORT EventType EventTypeFromXEvent(const XEvent& xev);
 
-// Get the EventFlags from a XEvent.
+// Gets the EventFlags from a XEvent.
 EVENTS_X_EXPORT int EventFlagsFromXEvent(const XEvent& xev);
 
-// Get the timestamp from a XEvent.
+// Gets the timestamp from a XEvent.
 EVENTS_X_EXPORT base::TimeDelta EventTimeFromXEvent(const XEvent& xev);
 
-// Get the location from a XEvent.  The coordinate system of the resultant
+// Gets the location from a XEvent.  The coordinate system of the resultant
 // |Point| has the origin at top-left of the "root window".  The nature of
 // this "root window" and how it maps to platform-specific drawing surfaces is
 // defined in ui/aura/root_window.* and ui/aura/window_tree_host*.
 EVENTS_X_EXPORT gfx::Point EventLocationFromXEvent(const XEvent& xev);
 
 // Gets the location in native system coordinate space.
 EVENTS_X_EXPORT gfx::Point EventSystemLocationFromXEvent(const XEvent& xev);
 
 // Returns the 'real' button for an event. The button reported in slave events
 // does not take into account any remapping (e.g. using xmodmap), while the
@@ skipping 39 matching lines @@
                                             float* vy,
                                             float* vx_ordinal,
                                             float* vy_ordinal,
                                             bool* is_cancel);
 
 EVENTS_X_EXPORT void ResetTimestampRolloverCountersForTesting();
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_X_EVENTS_X_UTILS_H_