Revert "Fix creating InjectedScript too early causing extension bindings not to work."

This reverts commit 6ff9795f2344c590eeccfc4ba87fde4218d080df.

Reverting this since it is causing failures in mac_rel
telemetry_unittests. tengs@ will re-land along with a
chromium side patch in order to resolve the issue.

BUG=
R=pfeldman@chromium.org

Review URL: https://codereview.chromium.org/22952005

git-svn-id: svn://svn.chromium.org/blink/trunk@156032 bbb929c8-8fbe-4397-9dbb-9b2b20218538