GitLab

```---------------------
Move more vector icons to respective directories and update code to
use gfx::VectorIcon structs instead of the VectorIconId enum.

Also add version of ImageButton::SetImage that takes a const ref image.

BUG=626786
Review-Url: https://codereview.chromium.org/2620613005
```

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Review-Url: https://codereview.chromium.org/2622893003
Cr-Commit-Position: refs/heads/master@{#442920}