Add layered buffer support to libui and libgui.

Bug: 31686534
Test: manual
Change-Id: Ia40270701467f4b785660324cad883e7da08989a
diff --git a/opengl/include/EGL/eglext.h b/opengl/include/EGL/eglext.h
index 8e69330..7cb608e 100644
--- a/opengl/include/EGL/eglext.h
+++ b/opengl/include/EGL/eglext.h
@@ -607,6 +607,7 @@
 
 #ifndef EGL_ANDROID_create_native_client_buffer
 #define EGL_ANDROID_create_native_client_buffer 1
+#define EGL_LAYER_COUNT_ANDROID 0x3434
 #define EGL_NATIVE_BUFFER_USAGE_ANDROID   0x3143
 #define EGL_NATIVE_BUFFER_USAGE_PROTECTED_BIT_ANDROID   0x00000001
 #define EGL_NATIVE_BUFFER_USAGE_RENDERBUFFER_BIT_ANDROID   0x00000002