Add canScroll bit to WebMouseWheelEvent

public/web/WebInputEvent.h

Index: public/web/WebInputEvent.h
diff --git a/public/web/WebInputEvent.h b/public/web/WebInputEvent.h
index ab7e4aba73b7186d8a9a70ec2efc8ebdd5da7618..3a137ce2665f9de5cfa4c835de790cada9358ae9 100644
--- a/public/web/WebInputEvent.h
+++ b/public/web/WebInputEvent.h
@@ -362,6 +362,13 @@ public:
     Phase momentumPhase;
 
     // See comment at the top of the file for why an int is used here.
+    // When false, this wheel event should not trigger scrolling (or any other default
+    // action) if the event goes unhandled by JavaScript. This is used, for example,
+    // when the browser decides the default behavior for Ctrl+Wheel should be to zoom
+    // instead of scroll.
+    int canScroll;
+
+    // See comment at the top of the file for why an int is used here.
     // Rubberbanding is an OSX visual effect. When a user scrolls the content
     // area with a track pad, and the content area is already at its limit in
     // the direction being scrolled, the entire content area is allowed to
@@ -391,6 +398,7 @@ public:
         , hasPreciseScrollingDeltas(false)
         , phase(PhaseNone)
         , momentumPhase(PhaseNone)
+        , canScroll(true)
         , canRubberbandLeft(true)
         , canRubberbandRight(true)
     {