Move logic of recording main thread scrolling reasons from cc to blink::ScrollManager

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 5f17029cb98046378feaba49cf27ce670e216dd1..9a0b92b03abc49f25d9f9095a844e3d5a97afbaf 100644
--- a/ui/events/blink/input_handler_proxy.cc
+++ b/ui/events/blink/input_handler_proxy.cc
@@ -552,6 +552,9 @@ void InputHandlerProxy::RecordMainThreadScrollingReasons(
     return;
   }
 
+  // NonCompositedScrollReasons should only be set on the main thread.
+  DCHECK(!cc::MainThreadScrollingReason::NonCompositedScrollReasons(reasons));
+
   // UMA_HISTOGRAM_ENUMERATION requires that the enum_max must be strictly
   // greater than the sample value. kMainThreadScrollingReasonCount doesn't
   // include the NotScrollingOnMain enum but the histograms do so adding