Add RecommendSampleRate to audio config test.

ppapi/tests/test_audio_config.cc

Index: ppapi/tests/test_audio_config.cc
===================================================================
--- ppapi/tests/test_audio_config.cc	(revision 142747)
+++ ppapi/tests/test_audio_config.cc	(working copy)
@@ -19,10 +19,22 @@
 }
 
 void TestAudioConfig::RunTests(const std::string& filter) {
+  RUN_TEST(RecommendSampleRate, filter);
   RUN_TEST(ValidConfigs, filter);
   RUN_TEST(InvalidConfigs, filter);
 }
 
+std::string TestAudioConfig::TestRecommendSampleRate() {
+  // Ask PPB_AudioConfig about the recommended sample rate.
+  PP_AudioSampleRate sample_rate = audio_config_interface_->RecommendSampleRate(
+      instance_->pp_instance());
+  ASSERT_TRUE(sample_rate == PP_AUDIOSAMPLERATE_NONE ||
+              sample_rate == PP_AUDIOSAMPLERATE_44100 ||
+              sample_rate == PP_AUDIOSAMPLERATE_48000);
+
+  PASS();
+}
+
 std::string TestAudioConfig::TestValidConfigs() {
   static const PP_AudioSampleRate kSampleRates[] = {
     PP_AUDIOSAMPLERATE_44100,