Open dream customization activity full-screen.

Current behavior is for the 3P dream settings activity to be embedded in
Settings. However, since the 3P activity may have a different theme than
Settings, we should open it in a separate fullscreen activity.

Test: locally on device
Bug: 215733289
Change-Id: I9ced996b47cede874a5c6e8ac0c84914693f527c

packages/SettingsLib/src/com/android/settingslib/dream/DreamBackend.java

@@ -402,7 +402,10 @@ public class DreamBackend {
         if (dreamInfo == null || dreamInfo.settingsComponentName == null) {
             return;
         }
-        uiContext.startActivity(new Intent().setComponent(dreamInfo.settingsComponentName));
+        final Intent intent = new Intent()
+                .setComponent(dreamInfo.settingsComponentName)
+                .addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
+        uiContext.startActivity(intent);
     }
 
     public void preview(DreamInfo dreamInfo) {