Add missing USED_FROM_MULTIPLE_THREADS(EventSource) declaration.

EventSource is available to Web Workers; declare its ThreadingTrait
accordingly.

R=
BUG=340522

Review URL: https://codereview.chromium.org/178913003

git-svn-id: svn://svn.chromium.org/blink/trunk@167818 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[oilpan] Move CSSRule to GC heap

BUG=

Review URL: https://codereview.chromium.org/150563006

git-svn-id: svn://svn.chromium.org/blink/trunk@167819 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Adjust composited clip rects properly for sub-pixel

This one-line change properly accumulates sub-pixel into the clip rect for
composited layers. The adjustment isn't needed for the other branch in the
code as the paint rect has already been properly aligned.

BUG=343850

Review URL: https://codereview.chromium.org/173053002

git-svn-id: svn://svn.chromium.org/blink/trunk@167820 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Move LiveNodeListBase class to its own header

Move LiveNodeListBase class to its own header instead of having it in the
LiveNodeList header. HTMLCollection also inherits from LiveNodeListBase
and is not interested in the LiveNodeList class.

There is still LiveNodeListBase code in HTMLCollection.cpp, this will be
moved in a follow-up patch.

R=esprehn, adamk

Review URL: https://codereview.chromium.org/177213010

git-svn-id: svn://svn.chromium.org/blink/trunk@167821 bbb929c8-8fbe-4397-9dbb-9b2b20218538