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This CL adds the basic elements needed to display the tab strip and
adds some basic placeholder HTML, CSS, and text to the UI.

Bug: 989131
Change-Id: I8f74dfb3b35b84ba349a6e6e44fd67fca2bbe117
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1726664
Commit-Queue: John Lee <johntlee@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683435}