[Telemetry] rename _needs_browser_restart_after_each_run -> <...>_each_page

Rename to reflect what this actually does.

BUG=350832
TBR=kbr@chromium.org

Review URL: https://codereview.chromium.org/192613002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255937 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255937