Fix problem when we did not play beginning of HTML5 audio stream in low latency mode.

media/audio/audio_output_controller.h

 // Copyright (c) 2011 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 MEDIA_AUDIO_AUDIO_OUTPUT_CONTROLLER_H_
 #define MEDIA_AUDIO_AUDIO_OUTPUT_CONTROLLER_H_
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 85 matching lines @@
     // AudioOutputController not yet played. This is used by SyncReader to
     // prepare more data and perform synchronization.
     virtual void UpdatePendingBytes(uint32 bytes) = 0;
 
     // Read certain amount of data into |data|. This method returns if some
     // data is available.
     virtual uint32 Read(void* data, uint32 size) = 0;
 
     // Close this synchronous reader.
     virtual void Close() = 0;
+
+    // Poll if data is ready.
+    // Not reliable, as there is no guarantee that renderer is "new-style"
+    // renderer that writes metadata into buffer. After several unsuccessful
+    // attempts caller should assume the data is ready even if that function
+    // returns false.
+    virtual bool DataReady() = 0;
   };
 
   virtual ~AudioOutputController();
 
   // Factory method for creating an AudioOutputController.
   // If successful, an audio controller thread is created. The audio device
   // will be created on the audio controller thread and when that is done
   // event handler will receive a OnCreated() call.
   static scoped_refptr<AudioOutputController> Create(
       EventHandler* event_handler,
@@ skipping 40 matching lines @@
 
   bool LowLatencyMode() const { return sync_reader_ != NULL; }
 
   ///////////////////////////////////////////////////////////////////////////
   // AudioSourceCallback methods.
   virtual uint32 OnMoreData(AudioOutputStream* stream, uint8* dest,
                             uint32 max_size, AudioBuffersState buffers_state);
   virtual void OnError(AudioOutputStream* stream, int code);
 
  private:
+  // We are polling sync reader if data became available.
+  static const int kPollNumAttempts;
+  static const int kPollPauseInMilliseconds;
+
   AudioOutputController(EventHandler* handler,
                         uint32 capacity, SyncReader* sync_reader);
 
   // The following methods are executed on the audio controller thread.
   void DoCreate(const AudioParameters& params);
   void DoPlay();
+  void PollAndStartIfDataReady();
   void DoPause();
   void DoFlush();
   void DoClose(const base::Closure& closed_task);
   void DoSetVolume(double volume);
   void DoReportError(int code);
 
   // Helper method to submit a OnMoreData() call to the event handler.
   void SubmitOnMoreData_Locked();
 
+  // Helper method that starts physical stream.
+  void StartStream();
+
   // |handler_| may be called only if |state_| is not kClosed.
   EventHandler* handler_;
   AudioOutputStream* stream_;
 
   // The current volume of the audio stream.
   double volume_;
 
   // |state_| is written on the audio controller thread and is read on the
   // hardware audio thread. These operations need to be locked. But lock
   // is not required for reading on the audio controller thread.
   State state_;
 
   AudioBuffersState buffers_state_;
 
   // The |lock_| must be acquired whenever we access |buffer_|.
   base::Lock lock_;
 
   media::SeekableBuffer buffer_;
 
   bool pending_request_;
 
   // SyncReader is used only in low latency mode for synchronous reading.
   SyncReader* sync_reader_;
 
   // The message loop of audio thread that this object runs on.
   MessageLoop* message_loop_;
 
+  // When starting stream we wait for data to become available.
+  // Number of times left.
+  int number_polling_attempts_left_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioOutputController);
 };
 
 }  // namespace media
 
 #endif  //  MEDIA_AUDIO_AUDIO_OUTPUT_CONTROLLER_H_