Avoid auto-resize re-entrancy problems.

ASSERT(needsLayout()) failed in various layout() methods. The reason is
that autoSizeIfEnabled() will re-enter FrameView::layout(), and upon return,
the rootForThisLayout RenderObject has already been layed out.

This CL moves the auto-sizing up to the top of FrameView::layout() to avoid
the re-entrancy problem with rootForThisLayout.

BUG=403743

Review URL: https://codereview.chromium.org/473903002

git-svn-id: svn://svn.chromium.org/blink/trunk@181258 bbb929c8-8fbe-4397-9dbb-9b2b20218538