Have the Performance interface inherit EventTarget

Have the Performance interface inherit EventTarget so that developers can
listen for the resourcetimingbufferfull event using addEventListener() and
to match the latest specification:
https://dvcs.w3.org/hg/webperf/raw-file/tip/specs/ResourceTiming/Overview.html#extensions-performance-interface

Corresponding discussion:
http://lists.w3.org/Archives/Public/public-web-perf/2013Jul/0004.html
http://lists.w3.org/Archives/Public/public-web-perf/2013Aug/0017.html

Also remove hack from the bindings generator as Performance was the only
interface with an EventHandler attribute which did not inherit from
EventTarget.

BUG=269927

Review URL: https://chromiumcodereview.appspot.com/22649003

git-svn-id: svn://svn.chromium.org/blink/trunk@155875 bbb929c8-8fbe-4397-9dbb-9b2b20218538