Use base::StringPairs where appropriate from src/extensions

extensions/common/permissions/permission_message_util.cc

Index: extensions/common/permissions/permission_message_util.cc
diff --git a/extensions/common/permissions/permission_message_util.cc b/extensions/common/permissions/permission_message_util.cc
index 070eabd2f0285cf3eb0efc8b50f8fa23f07acfa4..e98ad1f6ac6c8532a71d7f22888b5ec073f860cc 100644
--- a/extensions/common/permissions/permission_message_util.cc
+++ b/extensions/common/permissions/permission_message_util.cc
@@ -5,6 +5,7 @@
 #include "extensions/common/permissions/permission_message_util.h"
 
 #include "base/strings/string_number_conversions.h"
+#include "base/strings/string_split.h"
 #include "base/strings/utf_string_conversions.h"
 #include "extensions/common/permissions/permission_message.h"
 #include "extensions/common/permissions/permission_set.h"
@@ -92,7 +93,7 @@ std::set<std::string> GetDistinctHosts(const URLPatternSet& host_patterns,
   // Use a vector to preserve order (also faster than a map on small sets).
   // Each item is a host split into two parts: host without RCDs and
   // current best RCD.
-  typedef std::vector<std::pair<std::string, std::string> > HostVector;
+  typedef base::StringPairs HostVector;
   HostVector hosts_best_rcd;
   for (URLPatternSet::const_iterator i = host_patterns.begin();
        i != host_patterns.end();