Annotate libjingle_peerconnection_java with @Nullable.

Bug: webrtc:8881
Change-Id: Ida2ef6c003567d19529c21629c916ed40e8de3a6
Reviewed-on: https://webrtc-review.googlesource.com/63380
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Reviewed-by: Paulina Hensman <phensman@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22563}
diff --git a/sdk/android/api/org/webrtc/MediaConstraints.java b/sdk/android/api/org/webrtc/MediaConstraints.java
index fc0c9c2..76f0483 100644
--- a/sdk/android/api/org/webrtc/MediaConstraints.java
+++ b/sdk/android/api/org/webrtc/MediaConstraints.java
@@ -10,6 +10,7 @@
 
 package org.webrtc;
 
+import javax.annotation.Nullable;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -44,7 +45,7 @@
     }
 
     @Override
-    public boolean equals(Object other) {
+    public boolean equals(@Nullable Object other) {
       if (this == other) {
         return true;
       }