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- Change a vector of icons to small_icon and large_icon explicitly.
- Wrap Skbitmap to an Icon struct for future extension.

Bug: 963290
Change-Id: I6bd9459dc05e169e281659b67747a55c464e45bc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1758708Reviewed-by: David Trainor <dtrainor@chromium.org>
Reviewed-by: Xing Liu <xingliu@chromium.org>
Commit-Queue: Hesen Zhang <hesen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#688236}