GitLab

- Removed method declarations that are not defined.
- Removed PresentationFrameManager. There is not much reason to keep
  it since most of the logic is just delegating from PSDImpl.
- Push the URL validity check for screen availability to PSImpl.

BUG=736557

Review-Url: https://codereview.chromium.org/2958663002
Cr-Commit-Position: refs/heads/master@{#485437}