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This is a follow up to https://crrev.com/c/1423462.

Moving ForwardMessageToPortalHost to FrameNavigationControl associates
it with the Frame navigation messages and the legacy Frame IPC channel,
ensuring a defined ordering between postMessage and navigation messages.

Bug: 914120
Change-Id: I1fdb9a5be5b2d034764d28464aaeba955efc9320
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1536536Reviewed-by: Lucas Gadani <lfg@chromium.org>
Reviewed-by: Charlie Reis <creis@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Adithya Srinivasan <adithyas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#644386}