Retract GrRenderTarget from GrTestTarget

gm/rectangletexture.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 // This test only works with the GPU backend.
 
 #include "gm.h"
 
 #if SK_SUPPORT_GPU
 
 #include "GrContext.h"
+#include "GrGpu.h"
 #include "GrTest.h"
+#include "gl/GrGLContext.h"
 #include "SkBitmap.h"
 #include "SkGradientShader.h"
 #include "SkImage.h"
 
 namespace skiagm {
 class RectangleTexture : public GM {
 public:
     RectangleTexture() {
         this->setBGColor(0xFFFFFFFF);
     }
@@ skipping 154 matching lines @@
     }
 
 private:
     typedef GM INHERITED;
 };
 
 DEF_GM(return new RectangleTexture;)
 }
 
 #endif