Let Windows determine which mouse button is pressed.

        * platform/PlatformMouseEvent.h: Add message parameter to constructor.
        * platform/win/MouseEventWin.cpp:
        (WebCore::PlatformMouseEvent::PlatformMouseEvent): Use message
        parameter to determine which mouse button is pressed.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@16731 268f45cc-cd09-0410-ab3c-d52691b4dbfc