Document the split-screen action

The split-screen behavior is changed, so systemui doesn't
support this action with a single activity. We don't handle
this action by default from sc-v2. If SystemUI has any behavior
changed, they could register this action to support it.

Bug: 207056257
Test: presubmit pass
Change-Id: If569eff1ac52601e6b88324d7b47630a53e198f2

core/java/android/accessibilityservice/AccessibilityService.java

@@ -518,7 +518,9 @@ public abstract class AccessibilityService extends Service {
     public static final int GLOBAL_ACTION_POWER_DIALOG = 6;
 
     /**
-     * Action to toggle docking the current app's window
+     * Action to toggle docking the current app's window.
+     * <p>
+     * <strong>Note:</strong>  It is effective only if it appears in {@link #getSystemActions()}.
      */
     public static final int GLOBAL_ACTION_TOGGLE_SPLIT_SCREEN = 7;
 

services/accessibility/java/com/android/server/accessibility/SystemActionPerformer.java

@@ -288,8 +288,6 @@ public class SystemActionPerformer {
                     showGlobalActions();
                     return true;
                 }
-                case AccessibilityService.GLOBAL_ACTION_TOGGLE_SPLIT_SCREEN:
-                    return toggleSplitScreen();
                 case AccessibilityService.GLOBAL_ACTION_LOCK_SCREEN:
                     return lockScreen();
                 case AccessibilityService.GLOBAL_ACTION_TAKE_SCREENSHOT:
@@ -369,21 +367,6 @@ public class SystemActionPerformer {
         mWindowManagerService.showGlobalActions();
     }
 
-    private boolean toggleSplitScreen() {
-        final long token = Binder.clearCallingIdentity();
-        try {
-            StatusBarManagerInternal statusBarService = LocalServices.getService(
-                    StatusBarManagerInternal.class);
-            if (statusBarService == null) {
-                return false;
-            }
-            statusBarService.toggleSplitScreen();
-        } finally {
-            Binder.restoreCallingIdentity(token);
-        }
-        return true;
-    }
-
     private boolean lockScreen() {
         mContext.getSystemService(PowerManager.class).goToSleep(SystemClock.uptimeMillis(),
                 PowerManager.GO_TO_SLEEP_REASON_ACCESSIBILITY, 0);

services/tests/servicestests/src/com/android/server/accessibility/SystemActionPerformerTest.java

@@ -295,14 +295,6 @@ public class SystemActionPerformerTest {
         verify(mMockWindowManagerInternal).showGlobalActions();
     }
 
-    @Test
-    public void testToggleSplitScreen_legacy() {
-        setupWithRealContext();
-        mSystemActionPerformer.performSystemAction(
-                AccessibilityService.GLOBAL_ACTION_TOGGLE_SPLIT_SCREEN);
-        verify(mMockStatusBarManagerInternal).toggleSplitScreen();
-    }
-
     @Test
     public void testScreenshot_requestsFromScreenshotHelper_legacy() {
         setupWithMockContext();