Revert the revert. This change was not the cause of the failures, so relanding.

chrome/browser/sync/sync_ui_util.h

Index: chrome/browser/sync/sync_ui_util.h
===================================================================
--- chrome/browser/sync/sync_ui_util.h	(revision 110530)
+++ chrome/browser/sync/sync_ui_util.h	(working copy)
@@ -83,5 +83,12 @@
 void AddStringSyncDetails(ListValue* details, const std::string& stat_name,
                           const std::string& stat_value);
 
+// Returns a string describing the chrome version environment. Version format:
+// <Build Info> <OS> <Version number> (<Last change>)<channel or "-devel">
+// If version information is unavailable, returns "invalid."
+// TODO(zea): this approximately matches MakeUserAgentForSyncApi in
+// sync_backend_host.cc. Unify the two if possible.
+std::string GetVersionString();
+
 }  // namespace sync_ui_util
 #endif  // CHROME_BROWSER_SYNC_SYNC_UI_UTIL_H_