Updated error translation logic.

base/ios/ns_error_util.h

Index: base/ios/ns_error_util.h
diff --git a/base/ios/ns_error_util.h b/base/ios/ns_error_util.h
new file mode 100644
index 0000000000000000000000000000000000000000..101229208517e93a989b3aa704c9f8f4a3906333
--- /dev/null
+++ b/base/ios/ns_error_util.h
@@ -0,0 +1,25 @@
+// 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 BASE_IOS_NS_ERROR_UTIL_H_
+#define BASE_IOS_NS_ERROR_UTIL_H_
+
+@class NSError;
+
+namespace base {
+namespace ios {
+
+// Iterates through |error|'s underlying errors and returns the first error for
+// which there is no underlying error.
+NSError* GetFinalUnderlyingErrorFromError(NSError* error);
+
+// Returns a copy of |original_error| with |underlying_error| appended to the
+// end of its underlying error chain.
+NSError* ErrorWithAppendedUnderlyingError(NSError* original_error,
+                                          NSError* underlying_error);
+
+}  // namespace ios
+}  // namespace base
+
+#endif  // BASE_IOS_NS_ERROR_UTIL_H_