Force events to be non blocking if main thread is unresponsive.

third_party/WebKit/public/platform/WebInputEvent.h

Index: third_party/WebKit/public/platform/WebInputEvent.h
diff --git a/third_party/WebKit/public/platform/WebInputEvent.h b/third_party/WebKit/public/platform/WebInputEvent.h
index e22529c73b20e42cb62f2e95c23d4a4f355a7ca2..aa64ae7ad4ddcc5851e136d1bd190033eb3a347b 100644
--- a/third_party/WebKit/public/platform/WebInputEvent.h
+++ b/third_party/WebKit/public/platform/WebInputEvent.h
@@ -190,7 +190,7 @@ public:
     };
 
     // Indicates whether the browser needs to block on the ACK result for
-    // this event, and if not why note (for metrics/diagnostics purposes).
+    // this event, and if not, why (for metrics/diagnostics purposes).
     // These values are direct mappings of the values in PlatformEvent
     // so the values can be cast between the enumerations. static_asserts
     // checking this are in web/WebInputEventConversion.cpp.
@@ -204,6 +204,10 @@ public:
         // This value represents a state which would have normally blocking
         // but was forced to be non-blocking during fling; not cancelable.
         ListenersForcedNonBlockingDueToFling,
+        // This value represents a state which would have normally blocking but
+        // was forced to be non-blocking due to the main thread being
+        // unresponsive.
+        ListenersForcedNonBlockingDueToMainThreadResponsiveness,
     };
 
     // The rail mode for a wheel event specifies the axis on which scrolling is