Make some fields non-nullable in serial.mojom and data_stream.mojom.

extensions/renderer/api/serial/serial_api_unittest.cc

 // 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.
 
 #include "device/serial/serial_device_enumerator.h"
 #include "device/serial/serial_service_impl.h"
 #include "device/serial/test_serial_io_handler.h"
 #include "extensions/renderer/api_test_base.h"
 #include "grit/extensions_renderer_resources.h"
 
@@ skipping 15 matching lines @@
     result[0]->has_vendor_id = true;
     result[0]->product_id = 5678;
     result[0]->has_product_id = true;
     result[0]->display_name = "foo";
     result[1] = device::serial::DeviceInfo::New();
     result[1]->path = "another_device";
     // These IDs should be ignored.
     result[1]->vendor_id = 1234;
     result[1]->product_id = 5678;
     result[2] = device::serial::DeviceInfo::New();
+    result[2]->path = "";
     result[2]->display_name = "";
     return result.Pass();
   }
 };
 
 enum OptionalValue {
   OPTIONAL_VALUE_UNSET,
   OPTIONAL_VALUE_FALSE,
   OPTIONAL_VALUE_TRUE,
 };
@@ skipping 567 matching lines @@
 
 TEST_F(SerialApiTest, SetPausedUnknownConnectionId) {
   RunTest("serial_unittest.js", "testSetPausedUnknownConnectionId");
 }
 
 TEST_F(SerialApiTest, SendUnknownConnectionId) {
   RunTest("serial_unittest.js", "testSendUnknownConnectionId");
 }
 
 }  // namespace extensions