Do not expose is_null API for time values in Blink

third_party/WebKit/Source/core/input/GestureManager.cpp

 // Copyright 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.
 
 #include "core/input/GestureManager.h"
 
 #include "core/dom/Document.h"
 #include "core/dom/DocumentUserGestureToken.h"
 #include "core/editing/SelectionController.h"
 #include "core/events/GestureEvent.h"
@@ skipping 17 matching lines @@
       m_scrollManager(scrollManager),
       m_mouseEventManager(mouseEventManager),
       m_pointerEventManager(pointerEventManager),
       m_selectionController(selectionController) {
   clear();
 }
 
 void GestureManager::clear() {
   m_suppressMouseEventsFromGestures = false;
   m_longTapShouldInvokeContextMenu = false;
-  m_lastShowPressTimestamp = TimeTicks();
+  m_lastShowPressTimestamp.reset();
 }
 
 DEFINE_TRACE(GestureManager) {
   visitor->trace(m_frame);
   visitor->trace(m_scrollManager);
   visitor->trace(m_mouseEventManager);
   visitor->trace(m_pointerEventManager);
   visitor->trace(m_selectionController);
 }
 
@@ skipping 370 matching lines @@
   return WebInputEventResult::NotHandled;
 }
 
 FrameHost* GestureManager::frameHost() const {
   if (!m_frame->page())
     return nullptr;
 
   return &m_frame->page()->frameHost();
 }
 
-TimeTicks GestureManager::getLastShowPressTimestamp() const {
+WTF::Optional<WTF::TimeTicks> GestureManager::getLastShowPressTimestamp()
+    const {
   return m_lastShowPressTimestamp;
 }
 
 }  // namespace blink