Cleanup: Pass std::string as const reference from gpu/

gpu/config/gpu_blacklist_unittest.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/memory/scoped_ptr.h"
 #include "gpu/config/gpu_blacklist.h"
 #include "gpu/config/gpu_control_list_jsons.h"
 #include "gpu/config/gpu_feature_type.h"
 #include "gpu/config/gpu_info.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 const char kOsVersion[] = "10.6.4";
 
 namespace gpu {
 
 class GpuBlacklistTest : public testing::Test {
  public:
   GpuBlacklistTest() { }
 
   ~GpuBlacklistTest() override {}
 
   const GPUInfo& gpu_info() const {
     return gpu_info_;
   }
 
-  void RunFeatureTest(
-      const std::string feature_name, GpuFeatureType feature_type) {
+  void RunFeatureTest(const std::string& feature_name,
+                      GpuFeatureType feature_type) {
     const std::string json =
         "{\n"
         "  \"name\": \"gpu blacklist\",\n"
         "  \"version\": \"0.1\",\n"
         "  \"entries\": [\n"
         "    {\n"
         "      \"id\": 1,\n"
         "      \"os\": {\n"
         "        \"type\": \"macosx\"\n"
         "      },\n"
@@ skipping 80 matching lines @@
 
 GPU_BLACKLIST_FEATURE_TEST(PanelFitting,
                            "panel_fitting",
                            GPU_FEATURE_TYPE_PANEL_FITTING)
 
 GPU_BLACKLIST_FEATURE_TEST(GpuRasterization,
                            "gpu_rasterization",
                            GPU_FEATURE_TYPE_GPU_RASTERIZATION)
 
 }  // namespace gpu