assertion failed: !node || node->isElementNode() in WebCore::RenderBlock::clone

Regions based multi-column code now checks against cloning the FlowThread where the old code checked against cloning the multi-column div. 

Ported from https://bugs.webkit.org/show_bug.cgi?id=116614

BUG=242129

Review URL: https://chromiumcodereview.appspot.com/18762002

git-svn-id: svn://svn.chromium.org/blink/trunk@153630 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: Stop auto expanding retainers at Window object.

R=yurys@chromium.org

Review URL: https://codereview.chromium.org/18771002

git-svn-id: svn://svn.chromium.org/blink/trunk@153631 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: Animation frame details shows bogus heap size delta when contains GC event.

R=caseq@chromium.org, yurys@chromium.org

Review URL: https://codereview.chromium.org/18775002

git-svn-id: svn://svn.chromium.org/blink/trunk@153632 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Unofficial gardening. Tighten up some test expectations.

TBR=vsevik
BUG=254988,256226

Review URL: https://codereview.chromium.org/18553005

git-svn-id: svn://svn.chromium.org/blink/trunk@153634 bbb929c8-8fbe-4397-9dbb-9b2b20218538