Implement writing mic audio input data to file for debugging purposes.

content/browser/renderer_host/media/audio_input_debug_writer.cc

+// Copyright 2015 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 "content/browser/renderer_host/media/audio_input_debug_writer.h"
+
+#include "content/public/browser/browser_thread.h"
+#include "media/base/audio_bus.h"
+
+namespace content {
+
+AudioInputDebugWriter::AudioInputDebugWriter(base::File file)
+    : file_(file.Pass()),
+      interleaved_data_size_(0),
+      weak_factory_(this) {
+}
+
+AudioInputDebugWriter::~AudioInputDebugWriter() {
+  DCHECK_CURRENTLY_ON(BrowserThread::FILE);
+}
+
+void AudioInputDebugWriter::Write(scoped_ptr<media::AudioBus> data) {
+  BrowserThread::PostTask(
+      BrowserThread::FILE,
+      FROM_HERE,
+      base::Bind(&AudioInputDebugWriter::DoWrite,
+                 weak_factory_.GetWeakPtr(),
+                 base::Passed(&data)));
+}
+
+void AudioInputDebugWriter::DoWrite(scoped_ptr<media::AudioBus> data) {
+  DCHECK_CURRENTLY_ON(BrowserThread::FILE);
+
+  int data_size_bytes = 2 * data->frames() * data->channels();

[tommi (sloooow) - chröme, 2015/08/07 12:09:51]

Can you add a note here saying that we convert the data to 16 bit audio here and
change 2 to sizeof(int16)?

[Henrik Grunell, 2015/08/17 15:05:16]

Done.

+  if (!interleaved_data_ || interleaved_data_size_ != data_size_bytes) {
+    interleaved_data_.reset(new char[data_size_bytes]);
+    interleaved_data_size_ = data_size_bytes;
+  }
+
+  data->ToInterleaved(data->frames(), 2, interleaved_data_.get());
+  file_.WriteAtCurrentPos(interleaved_data_.get(), interleaved_data_size_);

[tommi (sloooow) - chröme, 2015/08/07 12:09:51]

nit: should the second parameter be data_size_bytes instead of
interleaved_data_size_?
At the moment they are the same, but I'm wondering if we should use
data_size_bytes for representing the amount of actually used bytes in the buffer
and interleaved_data_size_ for the size of the buffer itself.

If we do that, we can change the if() condition above to:
if (!interleaved_data_ || interleaved_data_size_ < data_size_bytes) {

[Henrik Grunell, 2015/08/17 15:05:16]

Sure, agree it's slightly better. Done.

+}
+
+}  // namspace content