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

media/audio/audio_output_controller.h

Index: media/audio/audio_output_controller.h
===================================================================
--- media/audio/audio_output_controller.h	(revision 104976)
+++ media/audio/audio_output_controller.h	(working copy)
@@ -103,6 +103,13 @@
 
     // 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();
@@ -163,12 +170,17 @@
   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);
@@ -178,6 +190,9 @@
   // 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_;
@@ -205,6 +220,10 @@
   // 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);
 };