Use screen rotation animation only if the display has content

It is unnecessary to run animation which is invisible to user.
Especially when adding a new display which is empty initially.

Also make sure that the leash for fade rotation animation is valid.
(For the case if the animation was canceled by other places.)

Bug: 213562756
Test: Either use legacy transition or shell transition.
      Start ScreenRecord and check logcat that there is no
      "Screen frozen" or "Creating Transition".
Change-Id: I8e905e4161a8eb768eadda4b160af57b7148f81d

services/core/java/com/android/server/wm/DisplayContent.java

@@ -1425,7 +1425,7 @@ class DisplayContent extends RootDisplayArea implements WindowManagerPolicy.Disp
             mWaitingForConfig = true;
             if (mTransitionController.isShellTransitionsEnabled()) {
                 requestChangeTransitionIfNeeded(changes, null /* displayChange */);
-            } else {
+            } else if (mLastHasContent) {
                 mWmService.startFreezingDisplay(0 /* exitAnim */, 0 /* enterAnim */, this);
             }
             sendNewConfiguration();
@@ -3222,6 +3222,7 @@ class DisplayContent extends RootDisplayArea implements WindowManagerPolicy.Disp
      */
     void requestChangeTransitionIfNeeded(@ActivityInfo.Config int changes,
             @Nullable TransitionRequestInfo.DisplayChange displayChange) {
+        if (!mLastHasContent) return;
         final TransitionController controller = mTransitionController;
         if (controller.isCollecting()) {
             if (displayChange != null) {
@@ -5090,6 +5091,11 @@ class DisplayContent extends RootDisplayArea implements WindowManagerPolicy.Disp
         return mLastHasContent;
     }
 
+    @VisibleForTesting
+    void setLastHasContent() {
+        mLastHasContent = true;
+    }
+
     void registerPointerEventListener(@NonNull PointerEventListener listener) {
         mPointerEventDispatcher.registerInputEventListener(listener);
     }

services/core/java/com/android/server/wm/FadeRotationAnimationController.java

@@ -256,7 +256,7 @@ public class FadeRotationAnimationController extends FadeAnimationController {
                     false /* applyFixedTransformationHint */);
             for (int i = mTargetWindowTokens.size() - 1; i >= 0; i--) {
                 final SurfaceControl leash = mTargetWindowTokens.valueAt(i);
-                if (leash != null) {
+                if (leash != null && leash.isValid()) {
                     rotator.applyTransform(t, leash);
                 }
             }
@@ -265,7 +265,7 @@ public class FadeRotationAnimationController extends FadeAnimationController {
         // Hide the windows immediately because a screenshot layer should cover the screen.
         for (int i = mTargetWindowTokens.size() - 1; i >= 0; i--) {
             final SurfaceControl leash = mTargetWindowTokens.valueAt(i);
-            if (leash != null) {
+            if (leash != null && leash.isValid()) {
                 t.setAlpha(leash, 0f);
             }
         }

services/tests/wmtests/src/com/android/server/wm/DisplayContentTests.java

@@ -1718,6 +1718,7 @@ public class DisplayContentTests extends WindowTestsBase {
     @Test
     public void testShellTransitRotation() {
         DisplayContent dc = createNewDisplay();
+        dc.setLastHasContent();
 
         final TestTransitionPlayer testPlayer = registerTestTransitionPlayer();
         final DisplayRotation dr = dc.getDisplayRotation();

services/tests/wmtests/src/com/android/server/wm/TransitionTests.java

@@ -488,6 +488,7 @@ public class TransitionTests extends WindowTestsBase {
         final TestTransitionPlayer player = registerTestTransitionPlayer();
 
         mDisplayContent.getDisplayRotation().setRotation(mDisplayContent.getRotation() + 1);
+        mDisplayContent.setLastHasContent();
         mDisplayContent.requestChangeTransitionIfNeeded(1 /* any changes */,
                 null /* displayChange */);
         final FadeRotationAnimationController fadeController =
@@ -536,6 +537,7 @@ public class TransitionTests extends WindowTestsBase {
                 null /* remoteTransition */, null /* displayChange */);
         mDisplayContent.getDisplayRotation().setRotation(mDisplayContent.getRotation() + 1);
         final int anyChanges = 1;
+        mDisplayContent.setLastHasContent();
         mDisplayContent.requestChangeTransitionIfNeeded(anyChanges, null /* displayChange */);
         transition.setKnownConfigChanges(mDisplayContent, anyChanges);
         final FadeRotationAnimationController fadeController =
@@ -550,9 +552,11 @@ public class TransitionTests extends WindowTestsBase {
         assertTrue(app.getTask().inTransition());
 
         final SurfaceControl.Transaction startTransaction = mock(SurfaceControl.Transaction.class);
+        final SurfaceControl leash = statusBar.mToken.getAnimationLeash();
+        doReturn(true).when(leash).isValid();
         player.onTransactionReady(startTransaction);
         // The leash should be unrotated.
-        verify(startTransaction).setMatrix(eq(statusBar.mToken.getAnimationLeash()), any(), any());
+        verify(startTransaction).setMatrix(eq(leash), any(), any());
 
         // The redrawn window will be faded in when the transition finishes. And because this test
         // only use one non-activity window, the fade rotation controller should also be cleared.