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

ui/events/base_event_utils.cc

Index: ui/events/base_event_utils.cc
diff --git a/ui/events/base_event_utils.cc b/ui/events/base_event_utils.cc
index c8eacb161b95d28604e0aef8df2efb28ba1034b8..d4545bc45c4560dddc39c2c217a5e0045dd39914 100644
--- a/ui/events/base_event_utils.cc
+++ b/ui/events/base_event_utils.cc
@@ -6,6 +6,7 @@
 
 #include "base/atomic_sequence_num.h"
 #include "base/command_line.h"
+#include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
@@ -43,6 +44,18 @@ bool IsSystemKeyModifier(int flags) {
          (EF_ALTGR_DOWN & flags) == 0;
 }
 
+base::LazyInstance<std::unique_ptr<base::TickClock>>::Leaky g_tick_clock =
+    LAZY_INSTANCE_INITIALIZER;
+
+base::TimeTicks EventTimeForNow() {
+  return g_tick_clock.Get() ? g_tick_clock.Get()->NowTicks()
+                            : base::TimeTicks::Now();
+}
+
+void SetEventTickClockForTesting(std::unique_ptr<base::TickClock> tick_clock) {
+  g_tick_clock.Get() = std::move(tick_clock);
+}
+
 double EventTimeStampToSeconds(base::TimeTicks time_stamp) {
   return (time_stamp - base::TimeTicks()).InSecondsF();
 }