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

BUG=263162
TEST=manual

Review URL: https://chromiumcodereview.appspot.com/22884002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@155947 bbb929c8-8fbe-4397-9dbb-9b2b20218538

primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs