Add missing accessor to ios PathProvider.

ios/chrome/browser/chrome_paths_internal.h

+// Copyright 2015 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 IOS_CHROME_BROWSER_CHROME_PATHS_INTERNAL_H_
+#define IOS_CHROME_BROWSER_CHROME_PATHS_INTERNAL_H_
+
+namespace base {
+class FilePath;
+}
+
+namespace ios {
+
+// Get the path to the user's cache directory. Note that Chrome on iOS cache
+// directories are actually subdirectories of this directory with names like
+// "Cache". This will always fill in |result| with a directory, sometimes
+// just |browser_state_dir|.
+void GetUserCacheDirectory(const base::FilePath& browser_state_dir,
+                           base::FilePath* result);
+
+}  // namespace ios
+
+#endif  // IOS_CHROME_BROWSER_CHROME_PATHS_INTERNAL_H_