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Some of the icons are now duplicated because updating all references to
them at once is very onerous --- often, updating one icon requires
updating many other related icons, e.g. all infobar icons. These will be
de-duped soon.

BUG=626786

Review-Url: https://codereview.chromium.org/2685683004
Cr-Commit-Position: refs/heads/master@{#450549}