[WIP] Inline help text for view diff page
Review Request #10910 — Created Feb. 21, 2020 and discarded — Latest diff uploaded
Add inline help text for revision selector, how to make comments, and the expander/collapse button in View Diff page
The inline help text for revision selector will show up when there is a revision selector(which means you need to have more than one version).
The inline help text for expander/collapse buttons will switch based on current button status.
Tested in Chrome, Firedox, Safari