Handle showWhenLocked on secondary displays

The keyguard has windows on the default display and the remote display
selected by MediaRouter. Keyguard occlusion only applies to the default
display. To make the activity showWhenLocked flag work on secondary
displays, pass the display id of the locked secondary display from the
SystemUi to KeyguardController and make its isKeyguardShowing method
take a displayId.

Test: android.server.cts.ActivityManagerDisplayTests
Test: #testSecondaryDisplayShowWhenLocked
Bug: 64994006
Change-Id: Ib31fc76e9df469e97a59a181f09d457ceed4ef5f
diff --git a/packages/SystemUI/src/com/android/keyguard/KeyguardDisplayManager.java b/packages/SystemUI/src/com/android/keyguard/KeyguardDisplayManager.java
index 8de1d31..2bc0e45c 100644
--- a/packages/SystemUI/src/com/android/keyguard/KeyguardDisplayManager.java
+++ b/packages/SystemUI/src/com/android/keyguard/KeyguardDisplayManager.java
@@ -15,6 +15,8 @@
  */
 package com.android.keyguard;
 
+import static android.view.Display.INVALID_DISPLAY;
+
 import android.app.Presentation;
 import android.content.Context;
 import android.content.DialogInterface;
@@ -28,16 +30,21 @@
 import android.view.View;
 import android.view.WindowManager;
 
+// TODO(multi-display): Support multiple external displays
 public class KeyguardDisplayManager {
     protected static final String TAG = "KeyguardDisplayManager";
     private static boolean DEBUG = KeyguardConstants.DEBUG;
+
+    private final ViewMediatorCallback mCallback;
+    private final MediaRouter mMediaRouter;
+    private final Context mContext;
+
     Presentation mPresentation;
-    private MediaRouter mMediaRouter;
-    private Context mContext;
     private boolean mShowing;
 
-    public KeyguardDisplayManager(Context context) {
+    public KeyguardDisplayManager(Context context, ViewMediatorCallback callback) {
         mContext = context;
+        mCallback = callback;
         mMediaRouter = (MediaRouter) mContext.getSystemService(Context.MEDIA_ROUTER_SERVICE);
     }
 
@@ -90,6 +97,7 @@
     };
 
     protected void updateDisplays(boolean showing) {
+        Presentation originalPresentation = mPresentation;
         if (showing) {
             MediaRouter.RouteInfo route = mMediaRouter.getSelectedRoute(
                     MediaRouter.ROUTE_TYPE_REMOTE_DISPLAY);
@@ -121,6 +129,13 @@
                 mPresentation = null;
             }
         }
+
+        // mPresentation is only updated when the display changes
+        if (mPresentation != originalPresentation) {
+            final int displayId = mPresentation != null
+                    ? mPresentation.getDisplay().getDisplayId() : INVALID_DISPLAY;
+            mCallback.onSecondaryDisplayShowingChanged(displayId);
+        }
     }
 
     private final static class KeyguardPresentation extends Presentation {