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This CL is the start of a refactor to pull update methods for
page action icons out of the LocationBar interface and into
a PageActionIconContainer interface so that page action icons
can live outside of the location bar.

Design doc: https://docs.google.com/document/d/18HJywSmw6JiYMxFTbP496ivilPblOT8A63V12ip3ymE/

Bug: 788051
Change-Id: I2ae0e289d1e777e7bde5d0d73094dbbc60b2109a
Reviewed-on: https://chromium-review.googlesource.com/1049126Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558378}