Cleanup: Pass std::string as const reference if possible

gpu/command_buffer/service/texture_manager_unittest.cc

 // Copyright (c) 2012 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 "gpu/command_buffer/service/texture_manager.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 463 matching lines @@
   static const GLuint kClient1Id = 1;
   static const GLuint kService1Id = 11;
   static const bool kUseDefaultTextures = false;
 
   TextureTestBase()
       : feature_info_(new FeatureInfo()) {
   }
   ~TextureTestBase() override { texture_ref_ = NULL; }
 
  protected:
-  void SetUpBase(MemoryTracker* memory_tracker, std::string extensions) {
+  void SetUpBase(MemoryTracker* memory_tracker, const std::string& extensions) {
     GpuServiceTest::SetUp();
     if (!extensions.empty()) {
       TestHelper::SetupFeatureInfoInitExpectations(gl_.get(),
                                                    extensions.c_str());
       feature_info_->Initialize();
     }
 
     manager_.reset(new TextureManager(memory_tracker,
                                       feature_info_.get(),
                                       kMaxTextureSize,
@@ skipping 1848 matching lines @@
   ExpectValid(GL_DEPTH_COMPONENT, GL_FLOAT, GL_DEPTH_COMPONENT32F);
   ExpectValid(GL_DEPTH_STENCIL, GL_UNSIGNED_INT_24_8, GL_DEPTH24_STENCIL8);
   ExpectValid(GL_DEPTH_STENCIL, GL_FLOAT_32_UNSIGNED_INT_24_8_REV,
               GL_DEPTH32F_STENCIL8);
 
   ExpectInvalid(GL_RGB_INTEGER, GL_INT, GL_RGBA8);
 }
 
 }  // namespace gles2
 }  // namespace gpu