GitLab

Componentize PrerenderObserver and PrerenderObserverList so WebLayer can use it
to support NoStatePrefetch.

Bug: 1096088
Change-Id: I6012e2a5699d21dc695cad913772f072986cd8f1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2308725Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Commit-Queue: Mugdha Lakhani <nator@chromium.org>
Cr-Commit-Position: refs/heads/master@{#790755}