WebTouchEvents have a slightly different behavior than QTouchEvent in
that the type of the event is TouchStart for each new point press,
while Qt sends a TouchBegin only for the first point press.

Since we already need to use ui::TouchEvent to be able to use
ui::GestureRecognizer, always do this conversion first to also let
UpdateWebTouchEventAfterDispatch chose the proper event type.
Some of the code from render_widget_host_view_aura.cc was copied into
render_widget_host_view_qt.cpp to fill the needed functionality.

Change-Id: Iab1ca0c449b5256a39b5479ce89b662d4e133935
Reviewed-by: Andras Becsi <andras.becsi@digia.com>