iwyu: Include stringprintf.h where appropriate, part 2.

chrome/browser/sync/glue/session_model_associator.h

Index: chrome/browser/sync/glue/session_model_associator.h
diff --git a/chrome/browser/sync/glue/session_model_associator.h b/chrome/browser/sync/glue/session_model_associator.h
index b9750130619debdc09e5c22f3bef6d9c4d647229..8c7972b5cbc373f908270e450d12d1dbb3eb13ed 100644
--- a/chrome/browser/sync/glue/session_model_associator.h
+++ b/chrome/browser/sync/glue/session_model_associator.h
@@ -15,7 +15,7 @@
 #include "base/gtest_prod_util.h"
 #include "base/memory/scoped_vector.h"
 #include "base/observer_list.h"
-#include "base/string_util.h"
+#include "base/stringprintf.h"
 #include "base/threading/non_thread_safe.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/sessions/session_id.h"
@@ -307,8 +307,7 @@ class SessionModelAssociator
   static inline std::string TabIdToTag(
       const std::string machine_tag,
       size_t tab_node_id) {
-    return StringPrintf("%s %"PRIuS"",
-        machine_tag.c_str(), tab_node_id);
+    return base::StringPrintf("%s %"PRIuS"", machine_tag.c_str(), tab_node_id);
   }
 
   // Initializes the tag corresponding to this machine.