Revert "Enable Activity Log to log creation of event handlers by extension content"

This reverts commit 7f2876b460e2ce0e6936fe5b766b0efe682dda59, aka r176757.

This change was causing failure in browser test ActivityLogApiTest.TriggerEvent

e.g.,

http://build.chromium.org/p/chromium.webkit/builders/Linux%20Tests/builds/37479/steps/browser_tests/logs/stdio

TBR=pmarch@chromium.org

Review URL: https://codereview.chromium.org/343543008

git-svn-id: svn://svn.chromium.org/blink/trunk@176781 bbb929c8-8fbe-4397-9dbb-9b2b20218538