Merge "[PiP2] Collect PiP candidate parent before request" into main

                    // Shell handles the request; see task supervisor's

                    // processStoppingAndFinishingActivities.

                    enterPipTransition.collect(r);

                    // Collecting the current task of the PiP-candidate activity prevents

                    // WindowAnimator from updating its surface visibility until the potential

                    // PiP transition formally starts.

                    enterPipTransition.collect(r.getTask());

                    getTransitionController().requestStartTransition(enterPipTransition,

                            r.getTask(), null /* remoteTransition */, null /* displayChange */);

                    // can run during finish, so partial