When focus transitions to or out of the PDF document, notify the PDF UI
of the same. PDF UI needs the information to draw/hide the focus
rectangle around the PDF document.
Unit tests have been added to validate the scenario.
Bug: 1069370
Change-Id: Ic25d79139ebf361d85168891580d14187610b0e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2061928
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Kevin Babbitt <kbabbitt@microsoft.com>
Commit-Queue: Ankit Kumar 🌪️ <ankk@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#771295}
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