Allow surfaceflinger to run vrflinger

* Allows surface flinger to switch in and out of vr mode

Bug: None
Test: Manually ran various vr test programs.
Change-Id: I15fbba0eb67cbcffeef41be31429550448a1db9c
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index 76c710a..12166a8 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -413,6 +413,10 @@
         }
     }
 
+    void clearHwcLayers() {
+        mHwcLayers.clear();
+    }
+
 #endif
     // -----------------------------------------------------------------------