Add a scrolling test for find-in-page

Turning on root-layer-scrolling caused find in page to break in Android
but wasn't turned up by tests. This CL adds a test to fill the gap. The
regression was incidentally fixed in r535827.

Also update TextFinder to use AbsoluteToRootFrame rather than
ContentsToRootFrame. The two are equivalent but I'd like to eventually
remove the Contents nomenclature since it can be easily confused for
being relative to the document origin.

This CL has no functional changes.

Bug: 810067
Change-Id: Idec7335f17e45184467ea14e403504efe7f9771c
Reviewed-on: https://chromium-review.googlesource.com/912510
Reviewed-by: Steve Kobes <skobes@chromium.org>
Reviewed-by: Paul Meyer <paulmeyer@chromium.org>
Commit-Queue: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536359}
3 files changed