Fix recording of kAnimatingScrollOnMain

ui/events/blink/input_handler_proxy.cc

Index: ui/events/blink/input_handler_proxy.cc
diff --git a/ui/events/blink/input_handler_proxy.cc b/ui/events/blink/input_handler_proxy.cc
index 377f6bddcbf73ce8b50cd054d5c9dc40524408dc..de95c206c3bc74cbff9a256364f8989462c913fe 100644
--- a/ui/events/blink/input_handler_proxy.cc
+++ b/ui/events/blink/input_handler_proxy.cc
@@ -427,6 +427,12 @@ void InputHandlerProxy::RecordMainThreadScrollingReasons(
        ++i) {
     unsigned val = 1 << i;
     if (reasons & val) {
+      if (val == cc::MainThreadScrollingReason::kAnimatingScrollOnMainThread) {
+        // We only want to record "animating scroll on main thread" reason if
+        // it's the only reason. Bail if that's not the case.
+        if (reasons & ~val)
+          continue;
+      }
       if (device == blink::WebGestureDeviceTouchscreen) {
         UMA_HISTOGRAM_ENUMERATION(
             kGestureHistogramName, i + 1,