Allow AudioRendererMixerInputs to be restarted after stopped.

media/base/audio_renderer_mixer_unittest.cc

Index: media/base/audio_renderer_mixer_unittest.cc
diff --git a/media/base/audio_renderer_mixer_unittest.cc b/media/base/audio_renderer_mixer_unittest.cc
index 857df2629e44b08372676f2a9b666b1a38fa18b6..cb58a0385580552df496d52609c253fcd1508b1c 100644
--- a/media/base/audio_renderer_mixer_unittest.cc
+++ b/media/base/audio_renderer_mixer_unittest.cc
@@ -396,8 +396,10 @@ TEST_P(AudioRendererMixerBehavioralTest, OnRenderError) {
 TEST_P(AudioRendererMixerBehavioralTest, OnRenderErrorPausedInput) {
   InitializeInputs(kMixerInputs);
 
-  for (size_t i = 0; i < mixer_inputs_.size(); ++i)
+  for (size_t i = 0; i < mixer_inputs_.size(); ++i) {
+    mixer_inputs_[i]->Start();
     EXPECT_CALL(*fake_callbacks_[i], OnRenderError()).Times(1);
+  }
 
   // Fire the error before attaching any inputs.  Ensure an error is recieved
   // even if the input is not connected.