Work on lining up the TextView and web page text.

Bug:3085564

Do not round the text size when applying it to the WebTextView,
so that it will better line up with the text shown on the web
page.

Modify the WebTextView paint to better match the paint used by
webkit.

Update the padding when the zoom level changes.

Change-Id: I284a6febcba2be21dc1ab3f74c6ab5751e1b19b6