Revert of Revert of Return GrGLContext from GrTestTarget

src/gpu/gl/GrGLGpu.h

Index: src/gpu/gl/GrGLGpu.h
diff --git a/src/gpu/gl/GrGLGpu.h b/src/gpu/gl/GrGLGpu.h
index 98d0ffcd33fda92912980e33ec0f7221b9ae6df5..4872db7309d656ccea5bb92b5767a99be2469681 100644
--- a/src/gpu/gl/GrGLGpu.h
+++ b/src/gpu/gl/GrGLGpu.h
@@ -109,8 +109,8 @@
                           const GrPipeline&,
                           const GrBatchTracker&) const override;
 
-    virtual const GrGLInterface* glInterfaceForTesting() const {
-        return this->glInterface();
+    const GrGLContext* glContextForTesting() const override {
+        return &this->glContext();
     }
 
 private:
@@ -300,7 +300,7 @@
 
     void unbindTextureFromFBO(GrGLenum fboTarget);
 
-    SkAutoTDelete<GrGLContext>  fGLContext;
+    SkAutoTUnref<GrGLContext>  fGLContext;
 
     void createCopyProgram();