surfaceflinger: manage RenderEngine with unique_ptr

Test: SurfaceFlinger_test
Change-Id: I603a399b88963acdcd154f721fe64bf59d9032fd
diff --git a/services/surfaceflinger/RenderEngine/GLES20RenderEngine.h b/services/surfaceflinger/RenderEngine/GLES20RenderEngine.h
index b96bfe0..84aa63c 100644
--- a/services/surfaceflinger/RenderEngine/GLES20RenderEngine.h
+++ b/services/surfaceflinger/RenderEngine/GLES20RenderEngine.h
@@ -60,9 +60,9 @@
 
 public:
     GLES20RenderEngine(uint32_t featureFlags); // See RenderEngine::FeatureFlag
+    virtual ~GLES20RenderEngine();
 
 protected:
-    virtual ~GLES20RenderEngine();
 
     virtual void dump(String8& result);
     virtual void setViewportAndProjection(size_t vpw, size_t vph,