Make NVPR a GL context option instead of a GL context

bench/nanobench.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef nanobench_DEFINED
 #define nanobench_DEFINED
 
@@ skipping 11 matching lines @@
 class SkCanvas;
 
 struct Config {
     const char* name;
     Benchmark::Backend backend;
     SkColorType color;
     SkAlphaType alpha;
     int samples;
 #if SK_SUPPORT_GPU
     GrContextFactory::GLContextType ctxType;
+    GrContextFactory::GLContextOptions ctxOptions;
     bool useDFText;
 #else
     int bogusInt;
+    int bogusIntOption;
     bool bogusBool;
 #endif
 };
 
 struct Target {
     explicit Target(const Config& c) : config(c) { }
     virtual ~Target() { }
 
     const Config config;
     SkAutoTDelete<SkSurface> surface;
@@ skipping 33 matching lines @@
 
     SkCanvas* getCanvas() const {
         if (!surface.get()) {
             return nullptr;
         }
         return surface->getCanvas();
     }
 };
 
 #endif  // nanobench_DEFINED