Make GrGpuResource::gpuMemorySize non-virtual w/ onGpuMemorySize virtual impl

src/gpu/gl/GrGLStencilBuffer.h

Index: src/gpu/gl/GrGLStencilBuffer.h
diff --git a/src/gpu/gl/GrGLStencilBuffer.h b/src/gpu/gl/GrGLStencilBuffer.h
index 024890ddd7ba30b433d3de39358d656c5da28301..53777e40c73343b599741c3cd5ea5a5acdb7e42f 100644
--- a/src/gpu/gl/GrGLStencilBuffer.h
+++ b/src/gpu/gl/GrGLStencilBuffer.h
@@ -37,8 +37,6 @@ public:
 
     virtual ~GrGLStencilBuffer();
 
-    virtual size_t gpuMemorySize() const SK_OVERRIDE;
-
     GrGLuint renderbufferID() const {
         return fRenderbufferID;
     }
@@ -51,6 +49,8 @@ protected:
     virtual void onAbandon() SK_OVERRIDE;
 
 private:
+    virtual size_t onGpuMemorySize() const SK_OVERRIDE;
+
     Format fFormat;
     // may be zero for external SBs associated with external RTs
     // (we don't require the client to give us the id, just tell