Allow unit tests to use a mock audio input controller.

media/audio/audio_input_controller.cc

Index: media/audio/audio_input_controller.cc
diff --git a/media/audio/audio_input_controller.cc b/media/audio/audio_input_controller.cc
index f94c00420da66b5eff1a0f15426eff165f3deec6..d64fb700f5fa5c1237f2da6ada73a0f49068e38b 100644
--- a/media/audio/audio_input_controller.cc
+++ b/media/audio/audio_input_controller.cc
@@ -15,6 +15,9 @@ const int kMaxSamplesPerPacket = kMaxSampleRate;
 
 namespace media {
 
+// static
+AudioInputController::Factory* AudioInputController::factory_ = NULL;
+
 AudioInputController::AudioInputController(EventHandler* handler)
     : handler_(handler),
       stream_(NULL),
@@ -40,6 +43,11 @@ scoped_refptr<AudioInputController> AudioInputController::Create(
       (samples_per_packet > kMaxSamplesPerPacket) || (samples_per_packet < 0))
     return NULL;
 
+  if (factory_) {
+    return factory_->Create(event_handler, format, channels, sample_rate,
+                            bits_per_sample, samples_per_packet);
+  }
+
   scoped_refptr<AudioInputController> controller = new AudioInputController(
       event_handler);