refactor AudioInputDevice to remove race condition.

content/content_renderer.gypi

Index: content/content_renderer.gypi
===================================================================
--- content/content_renderer.gypi	(revision 95453)
+++ content/content_renderer.gypi	(working copy)
@@ -68,6 +68,7 @@
         'renderer/media/audio_device.h',
         'renderer/media/audio_input_device.cc',
         'renderer/media/audio_input_device.h',
+        'renderer/media/audio_input_device_event_handler.h',
         'renderer/media/audio_input_message_filter.cc',
         'renderer/media/audio_input_message_filter.h',
         'renderer/media/audio_message_filter.cc',
@@ -217,6 +218,7 @@
         }],
         ['enable_webrtc==1', {
           'dependencies': [
+            '../third_party/webrtc/modules/audio_coding/main/source/audio_coding_module.gyp:audio_coding_module',
             '../third_party/webrtc/modules/video_capture/main/source/video_capture.gyp:video_capture_module',
             '../third_party/webrtc/system_wrappers/source/system_wrappers.gyp:system_wrappers',
             '../third_party/webrtc/video_engine/main/source/video_engine_core.gyp:video_engine_core',