Update PiP Flicker tests for content overlay

For some reason, the app icon overlay which is backed by hardware buffer
does not occlude the pipApp in the trace, though both the screen
recording and winscope trace suggest so.

Per discussion, we update the assertion that
- pipApp layer is always visible
- content overlay appears and then disappears
during the transition.

Bug: 265998256
Test: atest WMShellFlickerTests:EnterPipOnUserLeaveHintTest
Change-Id: I402aa1baf5c829fb12c30af659bc2827d65853a0

libs/WindowManager/Shell/tests/flicker/src/com/android/wm/shell/flicker/pip/EnterPipOnUserLeaveHintTest.kt

@@ -74,10 +74,18 @@ open class EnterPipOnUserLeaveHintTest(flicker: FlickerTest) : EnterPipTransitio
 
     @Presubmit
     @Test
-    override fun pipAppLayerOrOverlayAlwaysVisible() {
+    override fun pipAppLayerAlwaysVisible() {
         // pip layer in gesture nav will disappear during transition
         Assume.assumeFalse(flicker.scenario.isGesturalNavigation)
-        super.pipAppLayerOrOverlayAlwaysVisible()
+        super.pipAppLayerAlwaysVisible()
+    }
+
+    @Presubmit
+    @Test
+    override fun pipOverlayLayerAppearThenDisappear() {
+        // no overlay in gesture nav for non-auto enter PiP transition
+        Assume.assumeFalse(flicker.scenario.isGesturalNavigation)
+        super.pipOverlayLayerAppearThenDisappear()
     }
 
     @Presubmit

libs/WindowManager/Shell/tests/flicker/src/com/android/wm/shell/flicker/pip/EnterPipTransition.kt

@@ -43,13 +43,23 @@ abstract class EnterPipTransition(flicker: FlickerTest) : PipTransition(flicker)
     /** Checks [pipApp] layer remains visible throughout the animation */
     @Presubmit
     @Test
-    open fun pipAppLayerOrOverlayAlwaysVisible() {
+    open fun pipAppLayerAlwaysVisible() {
         flicker.assertLayers {
             this.isVisible(pipApp)
+        }
+    }
+
+    /** Checks the content overlay appears then disappears during the animation */
+    @Presubmit
+    @Test
+    open fun pipOverlayLayerAppearThenDisappear() {
+        val overlay = ComponentNameMatcher.PIP_CONTENT_OVERLAY
+        flicker.assertLayers {
+            this.notContains(overlay)
                 .then()
-                .isVisible(ComponentNameMatcher.PIP_CONTENT_OVERLAY)
+                .contains(overlay)
                 .then()
-                .isVisible(pipApp)
+                .notContains(overlay)
         }
     }