Fix DCHECK, which was happening due to un-initialized variables
for throttled subframes.

needs_forced_compositing_update_ could have been set, in cases
when a style update in a throttled frame caused destructive mutations
of compositing state that must be cleaned up or result in stale
pointers from cc.

needs_forced_compositing_update_ forces off throttling for a frame up to
the compositing step, for this reason. It is cleared during the compositing
update step. This means that ShouldThrottleRendering may return true after
this step when it returned false before.

Bug: 859596,863427

Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Idc4857b9f4a465f602e3bcc12a76e48d394a2689
Reviewed-on: https://chromium-review.googlesource.com/1141106
Reviewed-by: vmpstr <vmpstr@chromium.org>
Commit-Queue: Chris Harrelson <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576202}
2 files changed