Use WTF::TimeTicks to represent timestamp in Platform/Core event types

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

Index: third_party/WebKit/Source/core/input/TouchEventManager.cpp
diff --git a/third_party/WebKit/Source/core/input/TouchEventManager.cpp b/third_party/WebKit/Source/core/input/TouchEventManager.cpp
index 715b6d402ca01e469a5210943b55e5826c231707..bf1d0046d9d754114968bc8a89ffc2312d97fc5d 100644
--- a/third_party/WebKit/Source/core/input/TouchEventManager.cpp
+++ b/third_party/WebKit/Source/core/input/TouchEventManager.cpp
@@ -207,8 +207,8 @@ WebInputEventResult TouchEventManager::dispatchTouchEvents(
           m_frame->isMainFrame()) {
         // Record the disposition and latency of touch starts and first touch
         // moves before and after the page is fully loaded respectively.
-        int64_t latencyInMicros = static_cast<int64_t>(
-            (monotonicallyIncreasingTime() - event.timestamp()) * 1000000.0);
+        int64_t latencyInMicros =
+            (TimeTicks::Now() - event.timestamp()).InMicroseconds();
         if (event.cancelable()) {
           if (m_frame->document()->isLoadCompleted()) {
             DEFINE_STATIC_LOCAL(EnumerationHistogram,