Move RegisterContentSchemes from public url_constants into non-public url_schemes.

content/common/savable_url_schemes.h

+// Copyright (c) 2012 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 CONTENT_COMMON_SAVABLE_URL_SCHEMES_H_
+#define CONTENT_COMMON_SAVABLE_URL_SCHEMES_H_
+#pragma once
+
+namespace content {
+
+// Null terminated list of schemes that are savable. This function can be
+// invoked on any thread.
+const char* const* GetSavableSchemesInternal();
+
+// Intended for use only during initialization.
+void SetSavableSchemes(const char* const* savable_schemes);
+
+}  // namespace content
+
+#endif  // CONTENT_COMMON_SAVABLE_URL_SCHEMES_H_