Credential manager: Introduce platform interface.

public/platform/WebCredentialManagerError.h

Index: public/platform/WebCredentialManagerError.h
diff --git a/public/platform/WebCredentialManagerError.h b/public/platform/WebCredentialManagerError.h
new file mode 100644
index 0000000000000000000000000000000000000000..e3db57f3248e886e9aa3fe8ed931e0ad1d0d4aa3
--- /dev/null
+++ b/public/platform/WebCredentialManagerError.h
@@ -0,0 +1,31 @@
+// 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 WebCredentialManagerError_h
+#define WebCredentialManagerError_h
+
+#include "public/platform/WebString.h"
+
+namespace blink {
+
+struct WebCredentialManagerError {
+    enum ErrorType {
+        DisabledErrorType = 0,

[tkent, 2014/08/12 00:30:14]

The items should be ErrorTypeDisabled, ErrorTypeUnknown, and ErrorTypeLast.
http://www.chromium.org/blink/public-c-api#TOC-Naming

This rule is not so helpful for enums in classes/structs. However consistency is
important.

+        UnknownErrorType,
+        LastErrorType = UnknownErrorType
+    };
+
+    WebCredentialManagerError(ErrorType type, WebString message)
+        : errorType(type)
+        , errorMessage(message)
+    {
+    }
+
+    ErrorType errorType;
+    WebString errorMessage;
+};
+
+} // namespace blink
+
+#endif