Remove Document::IsRenderingReady

It is an alias of aveRenderBlockingResourcesLoaded, as of
the landing of commit ba6c026602da2b14b1e14b5fdf281822009cdc51

Change-Id: I36440d9e89f2ab64f0f769fa5d39a53ee3d40b75
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1515475
Reviewed-by: Stefan Zager <szager@chromium.org>
Commit-Queue: Chris Harrelson <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#639734}
8 files changed