Defer remove splash screen while device is locked

...and activity does not request showWhenLocked.
The splash screen won't contains secure information, so it's safe to
declared as showWhenLocked. But before remove starting window, if the
activity does not request showWhenLocked and device is locked, try to
trigger unoccluding animation, and keep app window hide until transition
animation finish.

Bug: 378088391
Bug: 383131643
Test: run simulate app repeatly, verify the app content won't be visible
during transition animation.

Merged-In: Id4db3772950059803883d00f9dd6b94aa98382f0
Change-Id: Id4db3772950059803883d00f9dd6b94aa98382f0

Author: wilsonshih

core/java/android/window/flags/windowing_frontend.aconfig

@@ -447,17 +447,6 @@ flag {
     }
 }
 
-flag {
-    name: "keep_app_window_hide_while_locked"
-    namespace: "windowing_frontend"
-    description: "Do not let app window visible while device is locked"
-    is_fixed_read_only: true
-    bug: "378088391"
-    metadata {
-        purpose: PURPOSE_BUGFIX
-    }
-}
-
 flag {
     name: "use_rt_frame_callback_for_splash_screen_transfer"
     namespace: "windowing_frontend"
@@ -564,4 +553,4 @@ flag {
     namespace: "lse_desktop_experience"
     description: "Adds support for trackpad back gestures on connected displays"
     bug: "382774299"
-}
+}

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

@@ -2708,7 +2708,8 @@ void associateStartingWindowWithTaskIfNeeded() {
      * This prevents briefly appearing the app context and causing secure concern.
      */
     void deferStartingWindowRemovalForKeyguardUnoccluding() {
-        if (mStartingData.mRemoveAfterTransaction != AFTER_TRANSITION_FINISH
+        if (mStartingData != null
+                && mStartingData.mRemoveAfterTransaction != AFTER_TRANSITION_FINISH
                 && isKeyguardLocked() && !canShowWhenLockedInner(this) && !isVisibleRequested()
                 && mTransitionController.inTransition(this)) {
             mStartingData.mRemoveAfterTransaction = AFTER_TRANSITION_FINISH;

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

@@ -2774,7 +2774,7 @@ void adjustStartingWindowFlags() {
             final boolean wasShowWhenLocked = (sa.flags & FLAG_SHOW_WHEN_LOCKED) != 0;
             final boolean removeShowWhenLocked = (mAttrs.flags & FLAG_SHOW_WHEN_LOCKED) == 0;
             sa.flags = (sa.flags & ~mask) | (mAttrs.flags & mask);
-            if (Flags.keepAppWindowHideWhileLocked() && wasShowWhenLocked && removeShowWhenLocked) {
+            if (wasShowWhenLocked && removeShowWhenLocked) {
                 // Trigger unoccluding animation if needed.
                 mActivityRecord.checkKeyguardFlagsChanged();
                 mActivityRecord.deferStartingWindowRemovalForKeyguardUnoccluding();