Force 8 kHz sampling rate on Android emulator.

BUG=None
R=henrika@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/55419004

Cr-Commit-Position: refs/heads/master@{#9310}

webrtc/modules/audio_device/android/java/src/org/webrtc/voiceengine/WebRtcAudioManager.java

@@ -179,6 +179,12 @@ class WebRtcAudioManager {
 
   // Returns the native output sample rate for this device's output stream.
   private int getNativeOutputSampleRate() {
+    // Override this if we're running on an old emulator image which only
+    // supports 8 kHz and doesn't support PROPERTY_OUTPUT_SAMPLE_RATE.
+    if (WebRtcAudioUtils.runningOnEmulator()) {
+      Logd("Running on old emulator, overriding sampling rate to 8 kHz.");
+      return 8000;
+    }
     if (!WebRtcAudioUtils.runningOnJellyBeanMR1OrHigher()) {
       return SAMPLE_RATE_HZ;
     }

webrtc/modules/audio_device/android/java/src/org/webrtc/voiceengine/WebRtcAudioUtils.java

@@ -64,6 +64,12 @@ public final class WebRtcAudioUtils {
         + ", id=" + Thread.currentThread().getId() + "]";
   }
 
+  // Returns true if we're running on emulator.
+  public static boolean runningOnEmulator() {
+    return Build.HARDWARE.equals("goldfish") &&
+        Build.BRAND.startsWith("generic_");
+  }
+
   // Returns true if the device is blacklisted for HW AEC usage.
   public static boolean deviceIsBlacklistedForHwAecUsage() {
     List<String> blackListedModels = Arrays.asList(BLACKLISTED_AEC_MODELS);