Move two generic string split functions from sync API to their own API in base/string_split.

base/string_split.h

Index: base/string_split.h
===================================================================
--- base/string_split.h	(revision 0)
+++ base/string_split.h	(revision 0)
@@ -0,0 +1,27 @@
+// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_STRING_SPLIT_H_
+#define BASE_STRING_SPLIT_H_
+
+#include <string>
+#include <utility>
+#include <vector>
+
+namespace base {
+
+bool SplitStringIntoKeyValues(
+    const std::string& line,
+    char key_value_delimiter,
+    std::string* key, std::vector<std::string>* values);
+
+bool SplitStringIntoKeyValuePairs(
+    const std::string& line,
+    char key_value_delimiter,
+    char key_value_pair_delimiter,
+    std::vector<std::pair<std::string, std::string> >* kv_pairs);
+
+}  // namespace base
+
+#endif  // BASE_STRING_SPLIT_H_