Refactor AppendToFile and WriteFileDescriptor

media/cast/test/simulator.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.
 
 // Simulate end to end streaming.
 //
 // Input:
 // --source=
 //   WebM used as the source of video and audio frames.
 // --output=
@@ skipping 168 matching lines @@
                                               true,
                                               media::cast::kMaxSerializedBytes,
                                               serialized_log.get(),
                                               &output_bytes);
 
   if (!success) {
     LOG(ERROR) << "Failed to serialize log.";
     return;
   }
 
-  if (AppendToFile(output_path, serialized_log.get(), output_bytes) == -1) {
+  if (!AppendToFile(output_path, serialized_log.get(), output_bytes)) {
     LOG(ERROR) << "Failed to append to log.";
   }
 }
 
 // Run simulation once.
 //
 // |output_path| is the path to write serialized log.
 // |extra_data| is extra tagging information to write to log.
 void RunSimulation(const base::FilePath& source_path,
                    const base::FilePath& output_path,
@@ skipping 337 matching lines @@
   values.SetBoolean("sim", true);
   values.SetString("sim-id", sim_id);
 
   std::string extra_data;
   base::JSONWriter::Write(&values, &extra_data);
 
   // Run.
   media::cast::RunSimulation(source_path, output_path, extra_data, model);
   return 0;
 }