Revert 286241 "Revert 286126 "Remove 'WebURLRequest::TargetType'..."

Revert 286241 "Revert 286126 "Remove 'WebURLRequest::TargetType'..."

This and related CLs were not the cause of apparent flakiness.
Apologies. Re-landing.

> Revert 286126 "Remove 'WebURLRequest::TargetType' from 'content:..."
>
> Believe this and related changes are the cause of recently introduced
> flakiness on the GPU bots. See Issue 390497.
>
> > Remove 'WebURLRequest::TargetType' from 'content::ResourceFetcher::Start'
> >
> > 'WebURLRequest::TargetType' has been dropped in Blink in favor of
> > 'RequestContext' and 'FrameType', matching the Fetch specification's
> > changes, and allowing both more granularity in various Blink-side checks
> > and more clarity around the thing that caused a request, and the frame
> > that the request affects.
> >
> > This CL should have zero practical effect, as it's simply hoisting the
> > translation work that 'WebURLRequest::setTargetType' is already doing
> > up into the content layer to bring us one step closer to removing the
> > concept entirely.
> >
> > BUG=390497
> >
> > Review URL: https://codereview.chromium.org/403313005
>
> TBR=mkwst@chromium.org
>
> Review URL: https://codereview.chromium.org/423163003

TBR=kbr@chromium.org

Review URL: https://codereview.chromium.org/423303003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@286338 0039d316-1c4b-4281-b951-d872f2087c98