[MPArch] Get rid of RenderFrameHostDelegate::GetMainFrameLastCommittedURL

GetMainFrameLastCommittedURL is not compatible with MPArch since it is
possible to have multiple FrameTrees in MPArch.

This CL gets rid of GetMainFrameLastCommittedURL which is implemented
on WebContentsImpl::GetMainFrameLastCommittedURL().

There are two callsites of GetMainFrameLastCommittedURL. Both
callsites essentially belong to RenderFrameHostImpl. So we don’t need
to get the main frame's last committed URL from WebContentsImpl that
is coarser than RenderFrameHostImpl.

- RenderFrameHostImpl::DidAddMessageToConsole()

DidAddMessageToConsole() is a member function of
RenderFrameHostImpl. So we don’t need to access to WebContentsImpl to
get the main frame's last committed URL. We can obtain the URL from
RenderFrameHostImpl.

- WebContentsImpl::GetRecordAggregateWatchTimeCallback()

GetRecordAggregateWatchTimeCallback() is called from
RenderFrameHostImpl::GetRecordAggregateWatchTimeCallback(). So this CL
gets the main frame's last committed URL from RenderFrameHostImpl, and
passes the URL via the argument of
GetRecordAggregateWatchTimeCallback().

Bug: 1240924
Change-Id: Icfba1f36e1783e716aa11b34de12122c532f797a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3102693
Commit-Queue: Minoru Chikamune <chikamune@chromium.org>
Reviewed-by: Rakina Zata Amni <rakina@chromium.org>
Reviewed-by: Nasko Oskov <nasko@chromium.org>
Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Cr-Commit-Position: refs/heads/main@{#913666}