touchui: Fix the maximization of a NativeWidgetGtk.
touchui: Fix the maximization of a NativeWidgetGtk.

Using gtk_widget_set_size_request leaves the window in a very weird state: it
changes the apparent size, but if the backing X window was larger before the
request, then it doesn't get resized to the smaller size. So subsequent calls to
get the bounds of the widget gets the pre-maximized larger size. So use the
proper API (gtk_window_resize) to do the window resizing.

BUG=none
TEST=manually

Review URL: http://codereview.chromium.org/7887019

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@101083 0039d316-1c4b-4281-b951-d872f2087c98

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