Treat error pages of initial iframe loads as initial iframe loads.

This also allows for getting rid of a FrameLoaderStateMachine state
after switching Document::finishedParsing's check to
committedFirstRealDocumentLoad.

Amend multiple-back-forward-entries.html to test this case more
and fix its expectations. The old expectations were missing the
child frame's history item.

BUG=368960

Review URL: https://codereview.chromium.org/260893003

git-svn-id: svn://svn.chromium.org/blink/trunk@173332 bbb929c8-8fbe-4397-9dbb-9b2b20218538
iPhone 5c marketing site repaints incorrectly with layer squashing

In the PaintsIntoGroupedBacking branch of
RenderLayerRepainter::setBackingNeedsRepaintInRect, we can
mistakenly use LayoutState if the transformedAncestor of the
RenderLayer is actually the RenderView. Unforunately,
LayoutState is not yet smart enough to handle repaints into
compositing containers, which means we'll compute the wrong
repaint rect for the squashed layer.

This CL adds a LayoutStateDisabler to this code path so that
we'll explicitly not use LayoutState. In the future, if we
make LayoutState smart enough to handle composited repaints,
we'll need to remove this disabler.

BUG=369478
R=leviw@chromium.org

Review URL: https://codereview.chromium.org/264713015

git-svn-id: svn://svn.chromium.org/blink/trunk@173333 bbb929c8-8fbe-4397-9dbb-9b2b20218538