Fix AudioCapturer implementation to read from audio pipe even when there are no active clients.

remoting/host/linux/pulseaudio_pipe_sink_reader.h

+// Copyright (c) 2012 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.
+
+#ifndef REMOTING_HOST_LINUX_PULSEAUDIO_PIPE_SINK_READER_H_
+#define REMOTING_HOST_LINUX_PULSEAUDIO_PIPE_SINK_READER_H_
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/ref_counted_memory.h"
+#include "base/message_loop.h"
+#include "base/observer_list_threadsafe.h"
+#include "base/time.h"
+#include "base/timer.h"
+
+class FilePath;
+
+namespace remoting {
+
+// PulseaudioPipeSinkReader class reads from a named pipe to which pulseaudio

[Wez, 2012/10/31 00:56:28]

nit: Suggest "PulseaudioPipeSinkReader reads raw audio samples from a configured
Pulseaudio sink via a named pipe, and delivers it to registered observers."

[Sergey Ulanov, 2012/10/31 18:41:24]

Done.

+// writes the sound that's being played back and then sends data to all
+// registered observers. ObserverListThreadSafe is used to send data to the

[Wez, 2012/10/31 00:56:28]

nit: Move this comment to the |observers_| member, e.g. "Used to deliver audio
samples to StreamObservers on the threads on which they registered."

[Sergey Ulanov, 2012/10/31 18:41:24]

I think that it's important for calling code on which thread the observer
interface is called. Moved this comment to AddObserver()

+// observers so each of them receives data on the thread on which it is
+// registered.
+class PulseaudioPipeSinkReader
+    : public base::RefCountedThreadSafe<PulseaudioPipeSinkReader>,
+      public MessageLoopForIO::Watcher {
+ public:
+  class StreamObserver {
+   public:
+    virtual void OnDataRead(scoped_refptr<base::RefCountedString> data) = 0;
+  };
+
+  // |task_runner| defines the IO thread on which the object will be reading
+  // data from the pipe.
+  PulseaudioPipeSinkReader(
+      scoped_refptr<base::SingleThreadTaskRunner> task_runner,
+      const FilePath& pipe_name);
+
+  // Functions to register and unregister observers.

[Wez, 2012/10/31 00:56:28]

nit: Suggest "Register or unregister an observer. An observer will receive
notifications only while registered."

[Sergey Ulanov, 2012/10/31 18:41:24]

Done.

+  void AddCapturer(StreamObserver* observer);
+  void RemoveCapturer(StreamObserver* observer);
+
+  // MessageLoopForIO::Watcher interface.
+  virtual void OnFileCanReadWithoutBlocking(int fd) OVERRIDE;
+  virtual void OnFileCanWriteWithoutBlocking(int fd) OVERRIDE;
+
+ private:
+  friend class base::RefCountedThreadSafe<PulseaudioPipeSinkReader>;
+  virtual ~PulseaudioPipeSinkReader();
+
+  void StartOnAudioThread(const FilePath& pipe_name);
+  void StartTimer();
+  void DoCapture();
+  void WaitForPipeReadable();
+
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+
+  int pipe_fd_;
+  base::RepeatingTimer<PulseaudioPipeSinkReader> timer_;
+  scoped_refptr<ObserverListThreadSafe<StreamObserver> > observers_;
+
+  // Time when capturing was started.
+  base::TimeTicks started_time_;
+
+  // Stream position of the last capture.
+  int64 last_capture_samples_;
+
+  // Bytes left from the previous read.
+  std::string left_over_bytes_;
+
+  MessageLoopForIO::FileDescriptorWatcher file_descriptor_watcher_;
+
+  DISALLOW_COPY_AND_ASSIGN(PulseaudioPipeSinkReader);
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_HOST_LINUX_PULSEAUDIO_PIPE_SINK_READER_H_