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

components/cdm/renderer/widevine_key_systems.cc

 // Copyright 2014 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 "components/cdm/renderer/widevine_key_systems.h"
 
 #include <string>
 #include <vector>
 
 #include "base/logging.h"
 #include "media/base/eme_constants.h"
 
 #include "widevine_cdm_version.h"  // In SHARED_INTERMEDIATE_DIR.
 
 #if defined(WIDEVINE_CDM_AVAILABLE)
 
 using media::KeySystemInfo;
 using media::SupportedCodecs;
 
 namespace cdm {
 
 // Return |name|'s parent key system.
-static std::string GetDirectParentName(std::string name) {
+static std::string GetDirectParentName(const std::string& name) {
   size_t last_period = name.find_last_of('.');
   DCHECK_GT(last_period, 0u);
   return name.substr(0u, last_period);
 }
 
 void AddWidevineWithCodecs(
     WidevineCdmType widevine_cdm_type,
     SupportedCodecs supported_codecs,
 #if defined(OS_ANDROID)
     SupportedCodecs supported_secure_codecs,
@@ skipping 50 matching lines @@
 #if defined(ENABLE_PEPPER_CDMS)
   info.pepper_type = kWidevineCdmPluginMimeType;
 #endif  // defined(ENABLE_PEPPER_CDMS)
 
   concrete_key_systems->push_back(info);
 }
 
 }  // namespace cdm
 
 #endif  // defined(WIDEVINE_CDM_AVAILABLE)