Validate that ui::Event::time_stamp comes from the same clock as TimeTicks::Now

ui/events/event_utils.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_EVENTS_EVENT_UTILS_H_
 #define UI_EVENTS_EVENT_UTILS_H_
 
 #include <stdint.h>
 
 #include <memory>
 
 #include "base/event_types.h"
 #include "base/strings/string16.h"
 #include "build/build_config.h"
 #include "ui/display/display.h"
+#include "ui/events/base_event_utils.h"
 #include "ui/events/event.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/events_export.h"
 #include "ui/events/keycodes/keyboard_codes.h"
 #include "ui/gfx/native_widget_types.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #endif
 
@@ skipping 24 matching lines @@
 
 // Get the EventFlags from a native event.
 EVENTS_EXPORT int EventFlagsFromNative(const base::NativeEvent& native_event);
 
 // Get the timestamp from a native event.
 // Note: This is not a pure function meaning that multiple applications on the
 // same native event may return different values.
 EVENTS_EXPORT base::TimeTicks EventTimeFromNative(
     const base::NativeEvent& native_event);
 
-// Create a timestamp based on the current time.
-// TODO(majidvp): Get rid of this in favor of call to TimeTicks::Now().
-// crbug.com/453559
-EVENTS_EXPORT base::TimeTicks EventTimeForNow();
+// Ensures that the event timestamp values are coming from the same underlying
+// monotonic clock as base::TimeTicks::Now() and if it is not then falls
+// back to using the current ticks for event timestamp.
+EVENTS_EXPORT void ValidateEventTimeClock(base::TimeTicks* timestamp);
 
 // Get the location from a native event.  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*.
 // TODO(tdresser): Return gfx::PointF here. See crbug.com/337827.
 EVENTS_EXPORT gfx::Point EventLocationFromNative(
     const base::NativeEvent& native_event);
 
 // Gets the location in native system coordinate space.
@@ skipping 101 matching lines @@
 // Update the native X11 event to correspond to the new button flags.
 EVENTS_EXPORT void UpdateX11EventForChangedButtonFlags(MouseEvent* event);
 #endif
 
 // Registers a custom event type.
 EVENTS_EXPORT int RegisterCustomEventType();
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_EVENT_UTILS_H_