Update hwui_unit_tests to support running with Vulkan backend.

Added Macros for RENDERTHREAD_TESTS which run these tests using specific backends.
RENDERTHREAD_TESTS - Runs OpenGL, SkiaGL, and SkiaVulkan
RENDERTHREAD_SKIA_TESTS - Runs SkiaGL and SkiaVulkan
RENDERTHREAD_OPENGL_TESTS - Runs OpenGL

Test: manual running of hwui_unit_tests

Change-Id: Ia7420ee7a38803a15e2d58394d14b38cae8208d3
diff --git a/libs/hwui/Properties.h b/libs/hwui/Properties.h
index b4a3118..6dc0cb3 100644
--- a/libs/hwui/Properties.h
+++ b/libs/hwui/Properties.h
@@ -318,11 +318,15 @@
     // any overhead they add
     static bool filterOutTestOverhead;
 
+    // Used for testing only to change the render pipeline.
+#ifdef HWUI_GLES_WRAP_ENABLED
+    static void overrideRenderPipelineType(RenderPipelineType);
+#endif
+
 private:
     static ProfileType sProfileType;
     static bool sDisableProfileBars;
     static RenderPipelineType sRenderPipelineType;
-
 }; // class Caches
 
 }; // namespace uirenderer