Remove const interfaces from content/public API.

Bug: 908139
Tbr: [email protected], [email protected], [email protected], [email protected]
Change-Id: Ic005b1cc50020f130fe216efcc1c01187bcaa9fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1680425
Commit-Queue: Lucas Gadani <[email protected]>
Reviewed-by: Avi Drissman <[email protected]>
Cr-Commit-Position: refs/heads/master@{#673393}
70 files changed