Move some content url constants to /url.

url/url_constants.h

Index: url/url_constants.h
diff --git a/url/url_constants.h b/url/url_constants.h
new file mode 100644
index 0000000000000000000000000000000000000000..9d184d9fa431bddf28dd97aefce84fbfcb0bb916
--- /dev/null
+++ b/url/url_constants.h
@@ -0,0 +1,17 @@
+// Copyright 2014 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 URL_URL_CONSTANTS_H_
+#define URL_URL_CONSTANTS_H_
+
+#include "url/url_export.h"
+
+namespace url {
+
+URL_EXPORT extern const char kHttpScheme[];
+URL_EXPORT extern const char kHttpsScheme[];
+
+}  // namespace url
+
+#endif  // URL_URL_CONSTANTS_H_