Partially automated revert of TreeScope::completeURL/baseURL logic

This reverts the work done in r164469, r165025, and r165098 to support
URL-completion at the TreeScope, rather than the Document, level.

TreeScope URL-completion logic (along with a settable ShadowRoot.baseURI
IDL attribute) was thought to be the solution to resource-loading in
custom elements that themselves were loaded from HTML imports. But in
attempting to implement that logic, enough issues were found to suggest
that this is not the right approach at this time.

See https://www.w3.org/Bugs/Public/show_bug.cgi?id=20976 for more discussion
of the trouble with specifying base URLs at the ShadowRoot level.

BUG=311682

Review URL: https://codereview.chromium.org/137853022

git-svn-id: svn://svn.chromium.org/blink/trunk@165255 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add a first pass of a class descendant invalidator, and a containing RuleSetAnalyzer

This allows us to (for some rule sets) only recalculate the elements
necessary when changing the class on an element, rather than then
entire subtree.

It's the first in a sequence of CLs to continue refactoring logic into
RuleSetAnalyzer, and expand the scope of targeted invalidation.

Review URL: https://codereview.chromium.org/129633003

git-svn-id: svn://svn.chromium.org/blink/trunk@165256 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove unused AudioNode::reset() and overrides.

BUG=none
TEST=none; no behavior changes.

Review URL: https://codereview.chromium.org/140353003

git-svn-id: svn://svn.chromium.org/blink/trunk@165257 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove LayoutIndicator which is basically dead code

The LayoutIndicator is being used for one assert which seems excessive.  The
original idea seems to be on hold and the other patches for the parallel layout
effort have been removed as well.

R=eseidel
BUG=289678

Review URL: https://codereview.chromium.org/140733004

git-svn-id: svn://svn.chromium.org/blink/trunk@165258 bbb929c8-8fbe-4397-9dbb-9b2b20218538