Define canonical enum for "HeliumResult" status values.

blimp/net/helium/helium_result.h

Index: blimp/net/helium/helium_result.h
diff --git a/blimp/net/helium/helium_result.h b/blimp/net/helium/helium_result.h
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+++ b/blimp/net/helium/helium_result.h
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+// Copyright 2016 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 BLIMP_NET_HELIUM_HELIUM_RESULT_H_
+#define BLIMP_NET_HELIUM_HELIUM_RESULT_H_
+
+#include "blimp/net/blimp_net_export.h"
+
+namespace blimp {
+
+// Defines the canonical list of Helium result codes.
+// HeliumResult::OK is the only non-error code.
+// All other codes are considered errors and are prefixed by ERR_.
+// See error_list.h for the unprefixed list of error codes.
+//
+// (Approach is inspired by net/base/net_errors.h)
+enum HeliumResult {
+  SUCCESS,
+#define HELIUM_ERROR(label, value) ERR_##label = value,
+#include "blimp/net/helium/helium_errors.h"
+#undef HELIUM_ERROR
+};
+
+// Gets a human-readable string representation of |result|.
+const char* BLIMP_NET_EXPORT HeliumResultToString(HeliumResult result);
+
+}  // namespace blimp
+
+#endif  // BLIMP_NET_HELIUM_HELIUM_RESULT_H_