Use a separate thread for audio capturing and encoding.

remoting/host/chromoting_host_context.h

Index: remoting/host/chromoting_host_context.h
diff --git a/remoting/host/chromoting_host_context.h b/remoting/host/chromoting_host_context.h
index 2e3480d69d3a1c50f59421615d2aad0d494ce494..149444a082adbe5d5424162098521ae8c1caeaf5 100644
--- a/remoting/host/chromoting_host_context.h
+++ b/remoting/host/chromoting_host_context.h
@@ -49,6 +49,9 @@ class ChromotingHostContext {
   // Task runner for the thread used to encode video streams.
   virtual base::SingleThreadTaskRunner* encode_task_runner();
 
+  // Task runner for the thread used for audio capture and encoding.
+  virtual base::SingleThreadTaskRunner* audio_task_runner();
+
   // Task runner for the thread used for network IO. This thread runs
   // a libjingle message loop, and is the only thread on which
   // libjingle code may be run.
@@ -80,6 +83,9 @@ class ChromotingHostContext {
   // A thread that hosts all encode operations.
   base::Thread encode_thread_;
 
+  // A thread that hosts audio capture and encoding.
+  base::Thread audio_thread_;
+
   // A thread that hosts input injection.
   base::Thread desktop_thread_;