A few small cleanning-ups.

1. Remove mDeferMultiTouch in WebView, it was for testing only but
we don't need it now since we always pass MultiTouch to WebKit.

2. Remove the use of mDeferMultiTouch in DRT tests.

3. Correct the index of getX(Y) for the second touch point in the
debug string of MotionEvent.

Change-Id: Ib63cfc5935af1a169ed26b2b138f74908492bc18