Change audio renderer to communicate with host using low latency codepath.

content/renderer/media/audio_renderer_impl.h

Index: content/renderer/media/audio_renderer_impl.h
===================================================================
--- content/renderer/media/audio_renderer_impl.h	(revision 91508)
+++ content/renderer/media/audio_renderer_impl.h	(working copy)
@@ -43,6 +43,7 @@
 #include "base/message_loop.h"
 #include "base/shared_memory.h"
 #include "base/synchronization/lock.h"
+#include "base/threading/simple_thread.h"
 #include "content/renderer/media/audio_message_filter.h"
 #include "media/audio/audio_io.h"
 #include "media/audio/audio_manager.h"
@@ -53,6 +54,7 @@
 
 class AudioRendererImpl : public media::AudioRendererBase,
                           public AudioMessageFilter::Delegate,
+                          public base::DelegateSimpleThread::Delegate,
                           public MessageLoop::DestructionObserver {
  public:
   // Methods called on Render thread ------------------------------------------
@@ -89,6 +91,14 @@
   virtual void ConsumeAudioSamples(scoped_refptr<media::Buffer> buffer_in);
 
  private:
+  // We are using either low- or high-latency code path.
+  enum LatencyType {
+    kUninitializedLatency = 0,
+    kLowLatency,
+    kHighLatency
+  };
+  static LatencyType latency_type_;
+
   // For access to constructor and IO thread methods.
   friend class AudioRendererImplTest;
   FRIEND_TEST_ALL_PREFIXES(AudioRendererImplTest, Stop);
@@ -114,6 +124,26 @@
   // Called on IO thread when message loop is dying.
   virtual void WillDestroyCurrentMessageLoop();
 
+  // DelegateSimpleThread::Delegate implementation.
+  virtual void Run();
+
+  // (Re-)starts playback.
+  void NotifyDataAvailableIfNecessary();
+
+  // Creates socket. Virtual so tests can override.
+  virtual void CreateSocket(base::SyncSocket::Handle socket_handle);
+
+  // Launching audio thread. Virtual so tests can override.
+  virtual void CreateAudioThread();
+
+  // Accessors used by tests.
+  LatencyType latency_type() {
+    return latency_type_;
+  }
+
+  // Should be called before any class instance is created.
+  static void set_latency_type(LatencyType latency_type);
+
   // Used to calculate audio delay given bytes.
   uint32 bytes_per_second_;
 
@@ -126,6 +156,12 @@
   scoped_ptr<base::SharedMemory> shared_memory_;
   uint32 shared_memory_size_;
 
+  // Low latency IPC stuff.
+  scoped_ptr<base::SyncSocket> socket_;
+
+  // That thread waits for audio input.
+  scoped_ptr<base::DelegateSimpleThread> audio_thread_;
+
   // Message loop for the IO thread.
   MessageLoop* io_loop_;