Grab mouse capture in the WM_TOUCH message handler in the omnibox.

This message is received in Windows 8 mode when we touch the window/click on it. It looks there is a bug
in Windows 8 where in after touching the window, the generated WM_LBUTTONDOWN messages goes to the window which had focus
previously. For e.g. if the focus was previously with the RenderWidgetHost window then it would get this message. The
handling for this message sets focus back to the RenderWidgetHost window, which causes the OSK to show up and disappear
when we touch the omnixbox.

Fix is to register the omnibox window for touch and grab capture when we receive a touch down and release it on touch up.
This ensures that subsequent mouse messages are sent to the omnibox and focus remains in the omnibox.

I also removed the WM_POINTERDOWN/WM_POINTERUP handlers as they are no longer functional given that we don't support
automatically popping up the OSK in desktop mode.

BUG=155155
R=sky
Review URL: https://codereview.chromium.org/11098077

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@161893 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed