Rename NoEventDispatchAssertion to EventDispatchForbiddenScope and move it to platform/

This is for consistency with ScriptForbiddenScope,
which is often used with EventDispatchForbiddenScope.

Review URL: https://codereview.chromium.org/446063007

git-svn-id: svn://svn.chromium.org/blink/trunk@180236 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Pull alerts from sheriff-o-matic.appspot.com instead of auto-sheriff.

At the moment alerts are being stored both at
http://sheriff-o-matic.appspot.com/alerts and
http://auto-sheriff.appspot.com/data . auto-sheriff will be turned
down, so stop reading alerts from there.

BUG=401358
NOTRY=true

Review URL: https://codereview.chromium.org/476593002

git-svn-id: svn://svn.chromium.org/blink/trunk@180237 bbb929c8-8fbe-4397-9dbb-9b2b20218538