Convert prefix search in UserScript code to use base::StartsWith()

extensions/browser/extension_user_script_loader.cc

 // Copyright 2015 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 "extensions/browser/extension_user_script_loader.h"
 
 #include <stddef.h>
 
 #include <set>
 #include <string>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
+#include "base/strings/string_util.h"
 #include "base/version.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/render_process_host.h"
 #include "extensions/browser/component_extension_resource_manager.h"
 #include "extensions/browser/content_verifier.h"
 #include "extensions/browser/extension_registry.h"
 #include "extensions/browser/extension_system.h"
 #include "extensions/browser/extensions_browser_client.h"
@@ skipping 69 matching lines @@
   // Localize the content.
   if (localization_messages) {
     std::string error;
     MessageBundle::ReplaceMessagesWithExternalDictionary(*localization_messages,
                                                          &content, &error);
     if (!error.empty())
       LOG(WARNING) << "Failed to replace messages in script: " << error;
   }
 
   // Remove BOM from the content.
-  std::string::size_type index = content.find(base::kUtf8ByteOrderMark);
-  if (index == 0)
+  if (base::StartsWith(content, base::kUtf8ByteOrderMark,
+                       base::CompareCase::SENSITIVE)) {
     script_file->set_content(content.substr(strlen(base::kUtf8ByteOrderMark)));
-  else
+  } else {
     script_file->set_content(content);
+  }
 
   return true;
 }
 
 SubstitutionMap* GetLocalizationMessages(
     const ExtensionUserScriptLoader::HostsInfo& hosts_info,
     const HostID& host_id) {
   ExtensionUserScriptLoader::HostsInfo::const_iterator iter =
       hosts_info.find(host_id);
   if (iter == hosts_info.end())
@@ skipping 110 matching lines @@
     const Extension* extension,
     UnloadedExtensionInfo::Reason reason) {
   hosts_info_.erase(HostID(HostID::EXTENSIONS, extension->id()));
 }
 
 void ExtensionUserScriptLoader::OnExtensionSystemReady() {
   SetReady(true);
 }
 
 }  // namespace extensions