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 0fec09a24220ea2205795ebf1736ad29ac99b562..4dc83426950a7c130d7d4e4b50df1f73604dd6be 100644
--- a/third_party/WebKit/Source/core/input/TouchEventManager.cpp
+++ b/third_party/WebKit/Source/core/input/TouchEventManager.cpp
@@ -206,8 +206,8 @@ 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,