Rename traits and mojo directory in //skia/public

This CL renames mojo to mojom and *_struct_traits.* to
*_mojom_traits.* in //skia/public.

*_struct_traits.* => *_mojom_traits.*
skia/public/interfaces => skia/public/mojom

Bug: 806965
Change-Id: I9b322799a7726149a1d685608b2e417e58107e0c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1722837
Commit-Queue: Miyoung Shin <[email protected]>
Reviewed-by: Nico Weber <[email protected]>
Reviewed-by: Scott Violet <[email protected]>
Reviewed-by: Kinuko Yasuda <[email protected]>
Cr-Commit-Position: refs/heads/master@{#682179}
87 files changed