Migrate calculation of hypertext from BrowserAccessibility to AXPlatformNode.

Bug: 703369
Change-Id: Icbab14a1d81201cde6d21a9ccf73e6ac9bd0286a
Reviewed-on: https://chromium-review.googlesource.com/678439
Reviewed-by: Nektarios Paisios <nektar@chromium.org>
Commit-Queue: Doug Turner <dougt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#504311}
7 files changed