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This goes through a code-path where the blob URL token was incorrectly
dropped, so make sure we copy the token from the old FrameLoadRequest to
the new FrameLoadRequest.

Adds a web-platform-test to verify this behavior, and enables the blob URL browser
tests to also run with MojoBlobURLs enabled. This browser test required another
bug fix in RenderFrameHostImpl.

Cq-Include-Trybots: luci.chromium.try:linux_mojo
Bug: 800901
Change-Id: I87eee70e784dd8cb273f8671f37b00d8a93d9543
Reviewed-on: https://chromium-review.googlesource.com/1102820Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568071}