Ensure that trackpad and trackpoint scrolling works on Windows desktop Aura with legacy trackpad drivers.

Legacy trackpad drivers like the older synaptics drivers have bugs where in they don't generate the WM_MOUSEWHEEL
messages for applications unless there is an entry for the application with the class name of the window in their
config file. If an entry does not exist here, these drivers expect the window to have the WS_VSCROLL/WS_HSCROLL style
to generate the legacy WM_VSCROLL/WM_HSCROLL messages.

This patch adds these styles to top level windows for Windows Aura. To ensure that Windows does not draw these
scrollbars, we hide them when the window size changes and readd them in a posted task which works correctly in our
testing.

Changes in this patch are as below:-
1. Add handlers to the HWNDMessageHandler class for the WM_VSCROLL/WM_HSCROLL messages.
2. Forward the scroll events to the HWNDMessageHandlerDelegate which then forwards it off to its delegate.
3. Miscellaneous fixes in the events code to allow the WM_VSCROLL/WM_HSCROLL messages to go through.

BUG=320849
R=cpu@chromium.org, sky@chromium.org, cpu, sky

Review URL: https://codereview.chromium.org/133053004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244295 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244295