Reland "Remove unit test harness methods referring to active/pending RenderViewHosts"

This is a reland of 2cebd52c9b516a07190b0d457606d033ca045166
Patchset 1 is what originally landed. In this reland, the only
change is to the CanCommitOrigin test to use the specified process.

Original change's description:
> Remove unit test harness methods referring to active/pending RenderViewHosts
>
> These are mostly unused. There are callers of
> RenderViewHostTestHarness::process, however no callers need the
> RenderProcessHost of a speculative RenderFrameHost, which makes further
> removals possible.
>
> Bug: 1015882
> Change-Id: Iff74517a43f5e1a7dbd057e4e871973d5bc17d71
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2930240
> Commit-Queue: Kevin McNee <mcnee@chromium.org>
> Auto-Submit: Kevin McNee <mcnee@chromium.org>
> Reviewed-by: Charlie Reis <creis@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#889357}

Bug: 1015882, 1217192
Change-Id: I6331a244e8247035cf0a791184c7a25cfff61d8e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2945756
Reviewed-by: Charlie Reis <creis@chromium.org>
Commit-Queue: Kevin McNee <mcnee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#890745}