APM: limit native sample rate to 16kHz on mobile.

Required by AECM which assert-fails on higher sample rates.

BUG=3259
R=andrew@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/21369005

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@6002 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/modules/audio_processing/include/audio_processing.h b/modules/audio_processing/include/audio_processing.h
index 6db1d12..68b679d 100644
--- a/modules/audio_processing/include/audio_processing.h
+++ b/modules/audio_processing/include/audio_processing.h
@@ -61,7 +61,12 @@
   bool enabled;
 };
 
+#if defined(ANDROID) || defined(IOS)
+// AECM only supports 8kHz & 16kHz.
+static const int kAudioProcMaxNativeSampleRateHz = 16000;
+#else
 static const int kAudioProcMaxNativeSampleRateHz = 32000;
+#endif
 
 // The Audio Processing Module (APM) provides a collection of voice processing
 // components designed for real-time communications software.