rlz: Add missing base:: prefix to StringPrintf call.

rlz/mac/lib/machine_id_mac.cc

Index: rlz/mac/lib/machine_id_mac.cc
diff --git a/rlz/mac/lib/machine_id_mac.cc b/rlz/mac/lib/machine_id_mac.cc
index 2198978a29740beebd6289aa3071cbdd57591524..fb9a34cb5149fd3ce3bc8417765578cf0615827d 100644
--- a/rlz/mac/lib/machine_id_mac.cc
+++ b/rlz/mac/lib/machine_id_mac.cc
@@ -122,7 +122,7 @@ bool GetRawMachineId(string16* data, int* more_data) {
 
   data->clear();
   if (GetMacAddress(mac_address, sizeof(mac_address))) {
-    *data += ASCIIToUTF16(StringPrintf("mac:%02x%02x%02x%02x%02x%02x",
+    *data += ASCIIToUTF16(base::StringPrintf("mac:%02x%02x%02x%02x%02x%02x",
         mac_address[0], mac_address[1], mac_address[2],
         mac_address[3], mac_address[4], mac_address[5]));
   }