Add stencil buffer to the EGL config

Change-Id: If76c0cd6127534d90f9526b75c0f8e56259c6722
diff --git a/libs/hwui/OpenGLRenderer.h b/libs/hwui/OpenGLRenderer.h
index ae355bb..d0394af 100644
--- a/libs/hwui/OpenGLRenderer.h
+++ b/libs/hwui/OpenGLRenderer.h
@@ -141,6 +141,8 @@
 
     SkPaint* filterPaint(SkPaint* paint);
 
+    ANDROID_API static uint32_t getStencilSize();
+
 protected:
     /**
      * Compose the layer defined in the current snapshot with the layer