SF: Define mock::RE::RenderEngine et al

This allows the unit test to use mocks in place of the normal
implementation.

Test: Builds
Bug: None
Change-Id: Iad51c4cf2373ef4313fc9ac77d1df4aa15d705ea
diff --git a/services/surfaceflinger/tests/unittests/MockRenderEngine.cpp b/services/surfaceflinger/tests/unittests/MockRenderEngine.cpp
new file mode 100644
index 0000000..e69f4cf
--- /dev/null
+++ b/services/surfaceflinger/tests/unittests/MockRenderEngine.cpp
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "MockRenderEngine.h"
+
+namespace android {
+namespace RE {
+namespace mock {
+
+// Explicit default instantiation is recommended.
+RenderEngine::RenderEngine() = default;
+RenderEngine::~RenderEngine() = default;
+
+Surface::Surface() = default;
+Surface::~Surface() = default;
+
+Image::Image() = default;
+Image::~Image() = default;
+
+} // namespace mock
+} // namespace RE
+} // namespace android