Disable ignore-pending-stylesheets mechanism

This disables the machinery of running layout while ignoring pending
stylesheets, and gets rid of display:none "placeholder" style. With
this patch, a forced layout that occurs while a stylesheet is pending
will resolve styles and run layout based on whatever style information
is available at the time.

There is a bunch of code cleanup to do after this patch,
but this should be the only functional change.

BUG=521692
R=chrishtr@chromium.org,futhark@chromium.org

Change-Id: I9b836c16aef67c43bd6170b23a39161302d6f810
Reviewed-on: https://chromium-review.googlesource.com/c/1334967
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609744}
9 files changed