Add canScroll bit to WebMouseWheelEvent

public/web/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 344 matching lines @@
 
     // See comment at the top of the file for why an int is used here.
     int scrollByPage;
 
     // See comment at the top of the file for why an int is used here.
     int hasPreciseScrollingDeltas;
     Phase phase;
     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
     // scroll slightly off screen, revealing a grey background. When the user
     // lets go, the content area snaps back into place. Blink is responsible
     // for this rubberbanding effect, but the embedder may wish to disable
     // rubber banding in the left or right direction, if the scroll should have
     // an alternate effect. The common case is that a scroll in the left or
     // right directions causes a back or forwards navigation, respectively.
     //
     // These flags prevent rubber banding from starting in a given direction,
     // but have no effect on an ongoing rubber banding. A rubber banding that
     // started in the vertical direction is allowed to continue in the right
     // direction, even if canRubberbandRight is 0.
     int canRubberbandLeft;
     int canRubberbandRight;
 
     WebMouseWheelEvent()
         : WebMouseEvent(sizeof(WebMouseWheelEvent))
         , deltaX(0.0f)
         , deltaY(0.0f)
         , wheelTicksX(0.0f)
         , wheelTicksY(0.0f)
         , accelerationRatioX(1.0f)
         , accelerationRatioY(1.0f)
         , scrollByPage(false)
         , hasPreciseScrollingDeltas(false)
         , phase(PhaseNone)
         , momentumPhase(PhaseNone)
+        , canScroll(true)
         , canRubberbandLeft(true)
         , canRubberbandRight(true)
     {
     }
 };
 
 // WebGestureEvent --------------------------------------------------------------
 
 class WebGestureEvent : public WebInputEvent {
 public:
@@ skipping 107 matching lines @@
         , causesScrollingIfUncanceled(false)
     {
     }
 };
 
 #pragma pack(pop)
 
 } // namespace blink
 
 #endif