Activity Logger Refactoring.

Enable Activity Logger to log issuing requests caused by extensions on pages.

BUG=388287

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=177761

Review URL: https://codereview.chromium.org/370763002

git-svn-id: svn://svn.chromium.org/blink/trunk@177845 bbb929c8-8fbe-4397-9dbb-9b2b20218538