Replace global portal token map with a search of the RenderFrameHostImpl set.

This is a linear search (and could be made with small effort to be more
efficient), but this set is expected to be extremely small in practice
(since each owns a WebContents, we are constrained by resources in any
event), so this is expected to be quite simple and quick in practice.

Bug: 964481
Change-Id: I030b641b79ea6604c468d1f9fa05a825714326e4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1951573
Commit-Queue: Jeremy Roman <jbroman@chromium.org>
Reviewed-by: Lucas Gadani <lfg@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#722267}
5 files changed