cleanup: pass string as const reference from c/b/extension/api

chrome/browser/extensions/api/file_system/file_system_api_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 "base/files/file_path.h"
 #include "base/strings/string_split.h"
+#include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/extensions/api/file_system/file_system_api.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/shell_dialogs/select_file_dialog.h"
 
 using extensions::FileSystemChooseEntryFunction;
 using extensions::api::file_system::AcceptOption;
 
 namespace {
 
 void CheckExtensions(const std::vector<base::FilePath::StringType>& expected,
     std::vector<base::FilePath::StringType>& actual) {
   EXPECT_EQ(expected.size(), actual.size());
   if (expected.size() != actual.size())
     return;
 
   for (size_t i = 0; i < expected.size(); ++i) {
     EXPECT_EQ(expected[i], actual[i]);
   }
 }
 
-AcceptOption* BuildAcceptOption(std::string description,
-    std::string mime_types,
-    std::string extensions) {
+AcceptOption* BuildAcceptOption(const std::string& description,
+                                const std::string& mime_types,
+                                const std::string& extensions) {
   AcceptOption* option = new AcceptOption();
 
   if (!description.empty())
     option->description.reset(new std::string(description));
 
   if (!mime_types.empty()) {
     option->mime_types.reset(new std::vector<std::string>());
     base::SplitString(mime_types, ',', option->mime_types.get());
   }
 
@@ skipping 22 matching lines @@
   bool acceptsAllTypes = false;
   FileSystemChooseEntryFunction::BuildFileTypeInfo(&file_type_info,
       base::FilePath::StringType(), NULL, &acceptsAllTypes);
   EXPECT_TRUE(file_type_info.include_all_files);
   EXPECT_TRUE(file_type_info.extensions.empty());
 
   // Test grouping of multiple types.
   file_type_info = ui::SelectFileDialog::FileTypeInfo();
   std::vector<linked_ptr<AcceptOption> > options;
   options.push_back(linked_ptr<AcceptOption>(BuildAcceptOption(
-      std::string(), "application/x-chrome-extension", "jso")));
+      base::EmptyString(), "application/x-chrome-extension", "jso")));
   acceptsAllTypes = false;
   FileSystemChooseEntryFunction::BuildFileTypeInfo(&file_type_info,
       base::FilePath::StringType(), &options, &acceptsAllTypes);
   EXPECT_FALSE(file_type_info.include_all_files);
   ASSERT_EQ(file_type_info.extensions.size(), (size_t) 1);
   EXPECT_TRUE(file_type_info.extension_description_overrides[0].empty()) <<
       "No override must be specified for boring accept types";
   // Note here (and below) that the expectedTypes are sorted, because we use a
   // set internally to generate the output: thus, the output is sorted.
   std::vector<base::FilePath::StringType> expectedTypes;
   expectedTypes.push_back(ToStringType("crx"));
   expectedTypes.push_back(ToStringType("jso"));
   CheckExtensions(expectedTypes, file_type_info.extensions[0]);
 
   // Test that not satisfying the extension will force all types.
   file_type_info = ui::SelectFileDialog::FileTypeInfo();
   options.clear();
-  options.push_back(linked_ptr<AcceptOption>(
-      BuildAcceptOption(std::string(), std::string(), "unrelated")));
+  options.push_back(linked_ptr<AcceptOption>(BuildAcceptOption(
+      base::EmptyString(), base::EmptyString(), "unrelated")));
   acceptsAllTypes = false;
   FileSystemChooseEntryFunction::BuildFileTypeInfo(&file_type_info,
       ToStringType(".jso"), &options, &acceptsAllTypes);
   EXPECT_TRUE(file_type_info.include_all_files);
 
   // Test multiple list entries, all containing their own types.
   file_type_info = ui::SelectFileDialog::FileTypeInfo();
   options.clear();
   options.push_back(linked_ptr<AcceptOption>(
-      BuildAcceptOption(std::string(), std::string(), "jso,js")));
+      BuildAcceptOption(base::EmptyString(), base::EmptyString(), "jso,js")));
   options.push_back(linked_ptr<AcceptOption>(
-      BuildAcceptOption(std::string(), std::string(), "cpp,cc")));
+      BuildAcceptOption(base::EmptyString(), base::EmptyString(), "cpp,cc")));
   acceptsAllTypes = false;
   FileSystemChooseEntryFunction::BuildFileTypeInfo(&file_type_info,
       base::FilePath::StringType(), &options, &acceptsAllTypes);
   ASSERT_EQ(file_type_info.extensions.size(), options.size());
 
   expectedTypes.clear();
   expectedTypes.push_back(ToStringType("js"));
   expectedTypes.push_back(ToStringType("jso"));
   CheckExtensions(expectedTypes, file_type_info.extensions[0]);
 
   expectedTypes.clear();
   expectedTypes.push_back(ToStringType("cc"));
   expectedTypes.push_back(ToStringType("cpp"));
   CheckExtensions(expectedTypes, file_type_info.extensions[1]);
 
   // Test accept type that causes description override.
   file_type_info = ui::SelectFileDialog::FileTypeInfo();
   options.clear();
   options.push_back(linked_ptr<AcceptOption>(
-      BuildAcceptOption(std::string(), "image/*", "html")));
+      BuildAcceptOption(base::EmptyString(), "image/*", "html")));
   acceptsAllTypes = false;
   FileSystemChooseEntryFunction::BuildFileTypeInfo(&file_type_info,
       base::FilePath::StringType(), &options, &acceptsAllTypes);
   ASSERT_EQ(file_type_info.extension_description_overrides.size(), (size_t) 1);
   EXPECT_FALSE(file_type_info.extension_description_overrides[0].empty()) <<
       "Accept type \"image/*\" must generate description override";
 
   // Test multiple accept types that cause description override causes us to
   // still present the default.
   file_type_info = ui::SelectFileDialog::FileTypeInfo();
   options.clear();
   options.push_back(linked_ptr<AcceptOption>(BuildAcceptOption(
-      std::string(), "image/*,audio/*,video/*", std::string())));
+      base::EmptyString(), "image/*,audio/*,video/*", base::EmptyString())));
   acceptsAllTypes = false;
   FileSystemChooseEntryFunction::BuildFileTypeInfo(&file_type_info,
       base::FilePath::StringType(), &options, &acceptsAllTypes);
   ASSERT_EQ(file_type_info.extension_description_overrides.size(), (size_t) 1);
   EXPECT_TRUE(file_type_info.extension_description_overrides[0].empty());
 
   // Test explicit description override.
   file_type_info = ui::SelectFileDialog::FileTypeInfo();
   options.clear();
   options.push_back(linked_ptr<AcceptOption>(
-      BuildAcceptOption("File Types 101", "image/jpeg", std::string())));
+      BuildAcceptOption("File Types 101", "image/jpeg", base::EmptyString())));
   acceptsAllTypes = false;
   FileSystemChooseEntryFunction::BuildFileTypeInfo(&file_type_info,
       base::FilePath::StringType(), &options, &acceptsAllTypes);
   EXPECT_EQ(file_type_info.extension_description_overrides[0],
       base::UTF8ToUTF16("File Types 101"));
 }
 
 TEST_F(FileSystemApiUnitTest, FileSystemChooseEntryFunctionSuggestionTest) {
   std::string opt_name;
   base::FilePath suggested_name;
@@ skipping 18 matching lines @@
   // TODO(thorogood): Fix this test on Windows.
   // Filter out absolute paths with no basename.
   opt_name = std::string("/");
   FileSystemChooseEntryFunction::BuildSuggestion(&opt_name, &suggested_name,
       &suggested_extension);
   EXPECT_FALSE(suggested_name.IsAbsolute());
   EXPECT_TRUE(suggested_name.MaybeAsASCII().empty());
   EXPECT_TRUE(suggested_extension.empty());
 #endif
 }