^, ^^, and ::distributed declared in inert shadow tree should not be applicable.

Tree-boundary crossing rules should consider whether their trees are active or not.
If not active, the rules should not match any elements.

BUG=341372
TEST=fast/dom/shadow/style-with-cat.html,fast/dom/shadow/style-with-hat.html,fast/dom/shadow/content-pseudo-element-in-inert-shadow.html

Review URL: https://codereview.chromium.org/156583003

git-svn-id: svn://svn.chromium.org/blink/trunk@167052 bbb929c8-8fbe-4397-9dbb-9b2b20218538