minor clean-up of the GLESRenderer

Change-Id: I978dea25b7687fbbbb283f09c24e115d9bad49a2
diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index f867e86..56bddd6 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -506,8 +506,10 @@
 void Layer::clearWithOpenGL(const sp<const DisplayDevice>& hw, const Region& clip,
         float red, float green, float blue, float alpha) const
 {
+    RenderEngine& engine(mFlinger->getRenderEngine());
     computeGeometry(hw, mMesh);
-    mFlinger->getRenderEngine().fillWithColor(mMesh, red, green, blue, alpha);
+    engine.setupFillWithColor(red, green, blue, alpha);
+    engine.drawMesh(mMesh);
 }
 
 void Layer::clearWithOpenGL(