base: Update the include paths of base/string_piece.h to its new location.

string_piece.h was moved into base/strings/ in r191206 -
https://chromiumcodereview.appspot.com/12982018/

[email protected]

Review URL: https://codereview.chromium.org/13374002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@191508 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/base/strings/sys_string_conversions_mac.mm b/base/strings/sys_string_conversions_mac.mm
index 4a38ad8..3650e4ef 100644
--- a/base/strings/sys_string_conversions_mac.mm
+++ b/base/strings/sys_string_conversions_mac.mm
@@ -10,7 +10,7 @@
 
 #include "base/mac/foundation_util.h"
 #include "base/mac/scoped_cftyperef.h"
-#include "base/string_piece.h"
+#include "base/strings/string_piece.h"
 
 namespace base {