Cleanup: Make ExtensionIconSet::Get return a const std::string& rather than a

extensions/common/manifest_handlers/icons_handler.cc

Index: extensions/common/manifest_handlers/icons_handler.cc
diff --git a/extensions/common/manifest_handlers/icons_handler.cc b/extensions/common/manifest_handlers/icons_handler.cc
index 518ff4065272f5b6e8862c0c4f1651be203b98e4..c7e6c61e31974b138dce731ac6fdf7c4b53a971b 100644
--- a/extensions/common/manifest_handlers/icons_handler.cc
+++ b/extensions/common/manifest_handlers/icons_handler.cc
@@ -37,7 +37,7 @@ ExtensionResource IconsInfo::GetIconResource(
     const Extension* extension,
     int size,
     ExtensionIconSet::MatchType match_type) {
-  std::string path = GetIcons(extension).Get(size, match_type);
+  const std::string& path = GetIcons(extension).Get(size, match_type);
   return path.empty() ? ExtensionResource() : extension->GetResource(path);
 }
 
@@ -45,7 +45,7 @@ ExtensionResource IconsInfo::GetIconResource(
 GURL IconsInfo::GetIconURL(const Extension* extension,
                            int size,
                            ExtensionIconSet::MatchType match_type) {
-  std::string path = GetIcons(extension).Get(size, match_type);
+  const std::string& path = GetIcons(extension).Get(size, match_type);
   return path.empty() ? GURL() : extension->GetResourceURL(path);
 }