Allow using task snapshot if new intent is same as previous one

There is no starting window while running AppLaunch tests after 3ee5fc0a.
The task snapshot was not allow to reuse due to the app was not started
via main intent.

Allow using task snapshot as long as the new intent is equals to the
previous intent. Unless the new intent contains extras that the app might
going to show something different from last time, like b/35099602.

Bug: 142144643
Test: run AppLaunch test
Test: no flash when open chrome incognito (b/35099602)
Change-Id: Id7acfe114d8b76de3527be28758c3f5e0d3dbc81