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

device/serial/data_sink_receiver.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/data_sink_receiver.h"
 
 #include <limits>
 
 #include "base/bind.h"
 #include "device/serial/async_waiter.h"
@@ skipping 71 matching lines @@
 void DataSinkReceiver::ShutDown() {
   shut_down_ = true;
   if (waiter_)
     waiter_.reset();
 }
 
 DataSinkReceiver::~DataSinkReceiver() {
 }
 
 void DataSinkReceiver::Init(mojo::ScopedDataPipeConsumerHandle handle) {
-  if (!handle.is_valid() || handle_.is_valid()) {
+  if (handle_.is_valid()) {
     DispatchFatalError();
     return;
   }
 
   handle_ = handle.Pass();
   StartWaiting();
 }
 
 void DataSinkReceiver::Cancel(int32_t error) {
   // If we have sent a ReportBytesSentAndError but have not received the
@@ skipping 194 matching lines @@
   MojoResult result =
       mojo::ReadDataRaw(handle, NULL, &num_bytes, MOJO_READ_DATA_FLAG_DISCARD);
   if (result != MOJO_RESULT_OK)
     return result;
   DCHECK(num_bytes <= bytes_to_flush_);
   bytes_to_flush_ -= num_bytes;
   return bytes_to_flush_ == 0 ? MOJO_RESULT_OK : MOJO_RESULT_SHOULD_WAIT;
 }
 
 }  // namespace device