Add win_gpu to the default set of try servers for Blink CLs.

This configuration is successfully handling the experimental load from
the Chromium and Blink commit queues. Expand its testing.

BUG=353864

Review URL: https://codereview.chromium.org/253873007

git-svn-id: svn://svn.chromium.org/blink/trunk@172839 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Scroll children should not apply the "comp-scroll" paint phase

This phase was incorrectly being applied to scroll
children and it was interfering with painting.

In particular, RenderLayer::paintLayerContents got
confused with the unexpected phase and did not paint the
negative z-order descendants.

Thank you, Ojan, for the fantastic repro case.

BUG=367277

Review URL: https://codereview.chromium.org/253733004

git-svn-id: svn://svn.chromium.org/blink/trunk@172840 bbb929c8-8fbe-4397-9dbb-9b2b20218538