broaden scale rejection to ignore all scales until a touch event

Inline image onload events also trigger a scroll change
(because the page becomes larger), so we can't just ignore the
first scale reading. So now ignore all scale readings until the
first thing that can actually *change* the scale-- a touch
event.

Bug: 6218921
Change-Id: I03476ca8c67a0d997ce067e74fc97612ffca4187
1 file changed