Use WebTextView overlay to render text fields/areas much faster

bug:5008210

Still has the following issues:

* colors are always black & white

* ignores centering, word wrap from text area

* gray background text (such as with instant search) and other textfield effects
  aren't shown

The DebugFlags.DRAW_WEBTEXTVIEW can still be used to overlay red text over the
input box.

Change-Id: I7f22321c31b9edbc5351cac13f2e17b0ee19d563