[MessageLoop]: Replace RunLoop-related ScopedNestableTaskAllower in /content/browser/renderer_host.

This CL replaces ScopedNestableTaskAllower with kNestableTasksAllowed passed
as argument to the RunLoop involved if any.
Only native nested loops should use ScopedNestableTaskAllower (soon to be deprecated).
For more details, see:
https://cs.chromium.org/chromium/src/base/message_loop/message_loop_current.h?sq=package:chromium&dr=CSs&g=0&l=159

A small step towards deleting MessageLoop.

This CL was generated with git cl split.
Refer to the top-level CL if necessary :
https://chromium-review.googlesource.com/c/chromium/src/+/1635819

Please CQ if LGTY!

This CL was uploaded by git cl split.

[email protected]

Bug: 766678
Change-Id: Ie73313c8719c0deb6f5556eedaf059b13dfd4c04
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1635525
Commit-Queue: Etienne Pierre-Doray <[email protected]>
Reviewed-by: Saman Sami <[email protected]>
Auto-Submit: Etienne Pierre-Doray <[email protected]>
Cr-Commit-Position: refs/heads/master@{#675254}
1 file changed