Actually trigger back action on Back Arrow fling

Currently, when the New Back Arrow is flung and the finger lifted, we do
not actually send the trigger event -- but we do if the finger is lifted
after coming to a "stop", i.e., a commit without a "fling".

To test, swipe from the right edge inwards, and release while your finger is in motion (as opposed to "stop moving, and then lift").

Bug: 240272871
Test: Manual
Change-Id: I81d6e6b1bb42c2cd12d14ae861ba8eb9f3081d11

packages/SystemUI/src/com/android/systemui/navigationbar/gestural/BackPanelController.kt

@@ -510,7 +510,6 @@ class BackPanelController private constructor(
     private fun playCommitBackAnimation() {
         // Check if we should vibrate again
         if (previousState != GestureState.FLUNG) {
-            backCallback.triggerBack()
             velocityTracker!!.computeCurrentVelocity(1000)
             val isSlow = abs(velocityTracker!!.xVelocity) < 500
             val hasNotVibratedRecently =
@@ -519,6 +518,10 @@ class BackPanelController private constructor(
                 vibratorHelper.vibrate(VibrationEffect.EFFECT_CLICK)
             }
         }
+        // Dispatch the actual back trigger
+        if (DEBUG) Log.d(TAG, "playCommitBackAnimation() invoked triggerBack() on backCallback")
+        backCallback.triggerBack()
+
         playAnimation(setGoneEndListener)
     }