extensions: Use stl utilities from the base namespace

extensions/common/extension_set.cc

Index: extensions/common/extension_set.cc
diff --git a/extensions/common/extension_set.cc b/extensions/common/extension_set.cc
index c4c15d4e1f2bc3b8f291f590f7be0b109a21583e..6d5657a39fda5cc9b0cc2c3773a9d23011a9516f 100644
--- a/extensions/common/extension_set.cc
+++ b/extensions/common/extension_set.cc
@@ -44,7 +44,7 @@ bool ExtensionSet::Contains(const std::string& extension_id) const {
 }
 
 bool ExtensionSet::Insert(const scoped_refptr<const Extension>& extension) {
-  bool was_present = ContainsKey(extensions_, extension->id());
+  bool was_present = base::ContainsKey(extensions_, extension->id());
   extensions_[extension->id()] = extension;
   if (!was_present && !modification_callback_.is_null())
     modification_callback_.Run(GetIDs());