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

third_party/WebKit/public/platform/WebInputEvent.h

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 172 matching lines @@
         IsComposing      = 1 << 14,
 
         AltGrKey         = 1 << 15,
         FnKey            = 1 << 16,
         SymbolKey        = 1 << 17,
 
         ScrollLockOn     = 1 << 18,
     };
 
     // 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.
     enum DispatchType {
         // Event can be canceled.
         Blocking,
         // Event can not be canceled.
         EventNonBlocking,
         // All listeners are passive; not cancelable.
         ListenersNonBlockingPassive,
         // 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
     // expected to stick. If this axis is set to Free, then scrolling is not
     // stuck to any axis.
     enum RailsMode {
         RailsModeFree       = 0,
         RailsModeHorizontal = 1,
         RailsModeVertical   = 2,
     };
@@ skipping 424 matching lines @@
         , uniqueTouchEventId(0)
     {
     }
 };
 
 #pragma pack(pop)
 
 } // namespace blink
 
 #endif