Assert event timestamp to be monotonic and not from future

third_party/WebKit/Source/core/events/Event.cpp

Index: third_party/WebKit/Source/core/events/Event.cpp
diff --git a/third_party/WebKit/Source/core/events/Event.cpp b/third_party/WebKit/Source/core/events/Event.cpp
index 3f4f9738ab5a41f8a1bf82f77ac5280491cbcf3d..8d201b7fe90764828b2c4be634c02b2e5488cb99 100644
--- a/third_party/WebKit/Source/core/events/Event.cpp
+++ b/third_party/WebKit/Source/core/events/Event.cpp
@@ -30,6 +30,7 @@
 #include "core/svg/SVGElement.h"
 #include "core/timing/DOMWindowPerformance.h"
 #include "core/timing/Performance.h"
+#include "platform/Histogram.h"
 #include "wtf/CurrentTime.h"
 
 namespace blink {
@@ -60,6 +61,13 @@ Event::Event()
 Event::Event(const AtomicString& eventType, bool canBubbleArg, bool cancelableArg, double platformTimeStamp)
     : Event(eventType, canBubbleArg, cancelableArg, ComposedMode::Scoped, platformTimeStamp)
 {
+    // Verify that timestamp is coming from the monotonic clock.
+    double delta = monotonicallyIncreasingTime() - platformTimeStamp;
+    bool hasValidTimebase = delta >= 0 && delta <= 60 * 1000;
+
+    DEFINE_STATIC_LOCAL(BooleanHistogram, histogram, ("Event.TimestampHasValidTimebase.Renderer"));
+    histogram.count(hasValidTimebase);
+    DCHECK(hasValidTimebase);
 }
 
 Event::Event(const AtomicString& eventType, bool canBubbleArg, bool cancelableArg, ComposedMode composedMode)