DO NOT MERGE. No direct Uri grants from system.

DO NOT MERGE. No direct Uri grants from system.

The system should never be extending Uri permission grants from
itself, since it automatically holds all the permissions.  Instead,
the system should always be a mediator between two specific app, and
it should be using startActivityAsCaller() if it needs to extend
permissions.

Blocking at this level fixes an entire class of confused deputy
security issues.

Test: builds, normal intent resolution UI works
Bug: 33019296, 32990341, 32879915, 32879772
Change-Id: Iaa57c393a386d8068e807d0dd0caccc89d8a11db