clean-up SurfaceFlinger a bit

- most methods on Layer didn't need to be virtual
- more consistency in naming drawing/current state

Change-Id: Ieb7b4951b40fc673b807994ed21ae4aea7281068
diff --git a/services/surfaceflinger/LayerDim.cpp b/services/surfaceflinger/LayerDim.cpp
index 36bafdb..f4adeeb 100644
--- a/services/surfaceflinger/LayerDim.cpp
+++ b/services/surfaceflinger/LayerDim.cpp
@@ -43,7 +43,7 @@
 
 void LayerDim::onDraw(const sp<const DisplayDevice>& hw, const Region& clip) const
 {
-    const State& s(drawingState());
+    const State& s(getDrawingState());
     if (s.alpha>0) {
         const GLfloat alpha = s.alpha/255.0f;
         const uint32_t fbHeight = hw->getHeight();
@@ -71,7 +71,7 @@
 }
 
 bool LayerDim::isVisible() const {
-    const Layer::State& s(drawingState());
+    const Layer::State& s(getDrawingState());
     return !(s.flags & layer_state_t::eLayerHidden) && s.alpha;
 }