Add rails to input wheel events.

Source/web/WebInputEvent.cpp

Index: Source/web/WebInputEvent.cpp
diff --git a/Source/web/WebInputEvent.cpp b/Source/web/WebInputEvent.cpp
index d08f7cf0ba9b6382319405f69bd5daa0bc1a7ade..a8f3c18cec6b52c843c7e0e8a91e7a14fa5aad28 100644
--- a/Source/web/WebInputEvent.cpp
+++ b/Source/web/WebInputEvent.cpp
@@ -51,7 +51,7 @@ struct SameSizeAsWebMouseEvent : public SameSizeAsWebInputEvent {
 };
 
 struct SameSizeAsWebMouseWheelEvent : public SameSizeAsWebMouseEvent {
-    int mousewheelData[10];
+    int mousewheelData[11];

[Ken Russell (switch to Gerrit), 2015/03/20 02:35:21]

These magic constants are awful. Can you think of a better way to handle them?

[ccameron, 2015/03/20 18:45:27]

This does seem pretty terrible -- do we know why this is even here? There's no
comment anywhere explaining this bizarre check.

[Rick Byers, 2015/03/20 18:53:52]

I always assumed they were just to ensure we get compile time failures if
someone accidentally increases the size of an IPC message.  I don't know where
they came from or if they're really serving any useful purpose.  Feel free to
file a bug and I can ask someone on input-dev to dig in and explore removing
them.  We recently removed another ugly IPC hack where for some reason we had
been avoiding 'bool' types for no good reason.  Could easily be WebKit legacy
somehow.

 };
 
 struct SameSizeAsWebGestureEvent : public SameSizeAsWebInputEvent {