Add a setting to control the DateExtension and add an histogram

I want to run an experiment and meassure the impact on unload handler
runtime depending on whether the date extension is on or off

BUG=299746
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/25265003

git-svn-id: svn://svn.chromium.org/blink/trunk@158617 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make releaseObjectGroup tolerate frontend disconneect.

BUG=260792

Review URL: https://codereview.chromium.org/23947002

git-svn-id: svn://svn.chromium.org/blink/trunk@158618 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Auto-rebaseline for r158608

http://src.chromium.org/viewvc/blink?view=revision&revision=158608

BUG=278044
TBR=pdr@chromium.org

Review URL: https://codereview.chromium.org/25381003

git-svn-id: svn://svn.chromium.org/blink/trunk@158619 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove a bogus assert in Document::setTitle().

m_titleElement can be either of HTMLTitleElement or SVGTitleElement. The
assertion was wrong.

BUG=301541
TEST=automated.

Review URL: https://codereview.chromium.org/25464002

git-svn-id: svn://svn.chromium.org/blink/trunk@158620 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add a comment to a subtle use of OwnPtr::release()

BUG=240653
R=dstockwell@chromium.org, dstockwell

Review URL: https://codereview.chromium.org/25040006

git-svn-id: svn://svn.chromium.org/blink/trunk@158621 bbb929c8-8fbe-4397-9dbb-9b2b20218538