Update protobuf to r428, part 1.

third_party/protobuf/src/google/protobuf/stubs/strutil.h

Index: third_party/protobuf/src/google/protobuf/stubs/strutil.h
===================================================================
--- third_party/protobuf/src/google/protobuf/stubs/strutil.h	(revision 216642)
+++ third_party/protobuf/src/google/protobuf/stubs/strutil.h	(working copy)
@@ -168,7 +168,19 @@
 LIBPROTOBUF_EXPORT void SplitStringUsing(const string& full, const char* delim,
                                          vector<string>* res);
 
+// Split a string using one or more byte delimiters, presented
+// as a nul-terminated c string. Append the components to 'result'.
+// If there are consecutive delimiters, this function will return
+// corresponding empty strings.  If you want to drop the empty
+// strings, try SplitStringUsing().
+//
+// If "full" is the empty string, yields an empty string as the only value.
 // ----------------------------------------------------------------------
+LIBPROTOBUF_EXPORT void SplitStringAllowEmpty(const string& full,
+                                              const char* delim,
+                                              vector<string>* result);
+
+// ----------------------------------------------------------------------
 // JoinStrings()
 //    These methods concatenate a vector of strings into a C++ string, using
 //    the C-string "delim" as a separator between components. There are two
@@ -453,5 +465,3 @@
 }  // namespace google
 
 #endif  // GOOGLE_PROTOBUF_STUBS_STRUTIL_H__
-
-