Add support for horizontal mouse wheel messages in Windows Desktop Aura.

ui/events/win/events_win.cc

Index: ui/events/win/events_win.cc
===================================================================
--- ui/events/win/events_win.cc	(revision 244940)
+++ ui/events/win/events_win.cc	(working copy)
@@ -180,6 +180,7 @@
     case WM_NCMOUSEMOVE:
       return ET_MOUSE_MOVED;
     case WM_MOUSEWHEEL:
+    case WM_MOUSEHWHEEL:
       return ET_MOUSEWHEEL;
     case WM_MOUSELEAVE:
     case WM_NCMOUSELEAVE:
@@ -268,7 +269,8 @@
 }
 
 gfx::Vector2d GetMouseWheelOffset(const base::NativeEvent& native_event) {
-  DCHECK(native_event.message == WM_MOUSEWHEEL);
+  DCHECK(native_event.message == WM_MOUSEWHEEL ||
+         native_event.message == WM_MOUSEHWHEEL);
   return gfx::Vector2d(0, GET_WHEEL_DELTA_WPARAM(native_event.wParam));

[sky, 2014/01/17 00:35:18]

WOuldn't a horizontal scroll effect the first parameter?

[ananta, 2014/01/17 00:47:17]

Doh. Should have seen that. Works in desktop Chrome on a page because RVHA uses
the native event to construct the wheel information.

Done.

 }