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

BUG=None 
TEST=base_unittests

Original patch by Thiago Farina
Original Review: http://codereview.chromium.org/464075

Review URL: http://codereview.chromium.org/502074

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@36774 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/base/base.gypi b/base/base.gypi
index ecdc0a0b..47789de 100644
--- a/base/base.gypi
+++ b/base/base.gypi
@@ -197,6 +197,8 @@
           'stl_util-inl.h',
           'string_piece.cc',
           'string_piece.h',
+          'string_split.cc',
+          'string_split.h',
           'string_tokenizer.h',
           'string_util.cc',
           'string_util.h',