::cue should use ShadowPseudo relation.

video::cue() matches some element in a shadow tree hosted by <video>.
So CSSSelector should be ::cue -(ShadowPseudo)-> video.

This is almost the same behavior as custom pseudo element.

BUG=266226

TEST=no test, because this patch is preparation one for fixing apply-author-styles. By this patch, no behavior changes. When fixing apply-author-styles, will add a new test.

Review URL: https://chromiumcodereview.appspot.com/21331002

git-svn-id: svn://svn.chromium.org/blink/trunk@155252 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fix baseline position when it is outside the element's box

Specifically, we shouldn't force the baseline to be inside
the element. IE and FF don't do this, and it's incompatible
with the CSS spec:

"The baseline of an 'inline-block' is the baseline of its last line box in the normal flow, unless it has either no in-flow line boxes or if its 'overflow' property has a computed value other than 'visible', in which case the baseline is the bottom margin edge."
(http://www.w3.org/TR/CSS21/visudet.html#leading)

It doesn't have a special case for "baseline is outside of the element's margin box".

This affects some tests in the obvious way which I marked as needing
rebaseline.

BUG=258650
R=leviw@chromium.org

Review URL: https://codereview.chromium.org/21124008

git-svn-id: svn://svn.chromium.org/blink/trunk@155253 bbb929c8-8fbe-4397-9dbb-9b2b20218538
MediaStream API: Update RTCDataChannel to match the specification
Just adding a bunch of attributes and deprecating one.

BUG=266333

Review URL: https://chromiumcodereview.appspot.com/21350002

git-svn-id: svn://svn.chromium.org/blink/trunk@155254 bbb929c8-8fbe-4397-9dbb-9b2b20218538