Fix some lint warnings on Android.

Bug: webrtc:6597
Change-Id: I215b319b3129949d12b74b11e6ec35eb123a1e5a
Reviewed-on: https://webrtc-review.googlesource.com/6781
Reviewed-by: Henrik Andreassson <henrika@webrtc.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20182}

sdk/android/src/java/org/webrtc/MediaCodecUtils.java

@@ -17,6 +17,8 @@ import android.media.MediaCodecInfo.CodecCapabilities;
 
 /** Container class for static constants and helpers used with MediaCodec. */
 @TargetApi(18)
+// We are forced to use the old API because we want to support API level < 21.
+@SuppressWarnings("deprecation")
 class MediaCodecUtils {
   private static final String TAG = "MediaCodecUtils";