Reland "Inline ResourceDispatcherHostImpl::CreateBaseResourceHandler"

This is a reland of ffc8179c8a7bca7404f1f9463331c9a8f54b69a5.
The original CL was reverted due to an infra issue.

Original change's description:
> Inline ResourceDispatcherHostImpl::CreateBaseResourceHandler
>
> Now it always creates a MojoAsyncResourceHandler, so there is no need to
> have a separate function.
>
> Bug: None
> Change-Id: Iafadf07f8dd5930d8de600ed87c0d2aa62a91038
> Reviewed-on: https://chromium-review.googlesource.com/1169034
> Reviewed-by: Charlie Harrison <[email protected]>

Bug: None
Change-Id: If915cdf70ae06088b7eea366972472d22b71c28e
Tbr: [email protected]
Reviewed-on: https://chromium-review.googlesource.com/1173591
Reviewed-by: Yutaka Hirano <[email protected]>
Commit-Queue: Yutaka Hirano <[email protected]>
Cr-Commit-Position: refs/heads/master@{#582805}
2 files changed