GitLab

Adds functions for converting from gfx::Rect to pp::Rect, and from
gfx::Size to pp::Size.

Also makes a few extra improvements:
1. Adds unit tests.
2. Orders Point functions before Rect and Size, for consistency.

Bug: 1101101
Change-Id: I5e3b0a3e5361d799103c9771ac29a9c0b74df999
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2304931
Commit-Queue: K. Moon <kmoon@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#789694}