Convert utility process WiFi Credentials IPC to mojo

chrome/common/extensions/wifi_credentials_getter.mojom

+// Copyright 2017 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.
+
+// WiFi credentials interface provided by the utility process and exposed
+// by mojo policy control to the chrome browser process on OS_WIN.
+
+module extensions.mojom;
+
+interface WiFiCredentialsGetter {
+  // OS_WIN: Get plain-text WiFi credentials from the system (requires UAC
+  // privilege elevation). Returns |success| false if an error occurred or
+  // |success| true and the result in |key_data|.
+  GetWiFiCredentials(string ssid) => (bool success, string key_data);
+};