Change ui::Event::time_stamp from TimeDelta to TimeTicks

ui/events/base_event_utils.h

Index: ui/events/base_event_utils.h
diff --git a/ui/events/base_event_utils.h b/ui/events/base_event_utils.h
index 6f07b09f81b0b480bb386007b4b53a2677fe75a5..74902516029ee8af5503075414fb485aa68b18d8 100644
--- a/ui/events/base_event_utils.h
+++ b/ui/events/base_event_utils.h
@@ -9,6 +9,10 @@
 
 #include "ui/events/events_base_export.h"
 
+namespace base {
+class TimeTicks;
+}
+
 // Common functions to be used for all platforms.
 namespace ui {
 
@@ -18,6 +22,17 @@ EVENTS_BASE_EXPORT uint32_t GetNextTouchEventId();
 // Checks if |flags| contains system key modifiers.
 EVENTS_BASE_EXPORT bool IsSystemKeyModifier(int flags);
 
+// Converts an event timestamp ticks to seconds (floating point representation).
+// WARNING: This should only be used when interfacing with platform code that
+// does not use base::Time* types.
+EVENTS_BASE_EXPORT double EventTimeStampToSeconds(base::TimeTicks time_stamp);
+
+// Converts an event timestamp in seconds to TimeTicks.
+// WARNING: This should only be used when interfacing with platform code that
+// does not use base::Time* types.
+EVENTS_BASE_EXPORT base::TimeTicks EventTimeStampFromSeconds(
+    double time_stamp_seconds);
+
 }  // namespace ui
 
 #endif  // UI_EVENTS_BASE_EVENT_UTILS_H_