Android: Generate JNI code for RTCStats

Bug: webrtc:8278
Change-Id: I183cec54ec3e97894db7f26e365eb9941a1ab458
Reviewed-on: https://webrtc-review.googlesource.com/25660
Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20879}

sdk/android/api/org/webrtc/RTCStatsReport.java

@@ -52,4 +52,11 @@ public class RTCStatsReport {
     builder.append(" ] }");
     return builder.toString();
   }
+
+  // TODO(bugs.webrtc.org/8557) Use ctor directly with full Map type.
+  @SuppressWarnings("unchecked")
+  @CalledByNative
+  private static RTCStatsReport create(long timestampUs, Map stats) {
+    return new RTCStatsReport(timestampUs, stats);
+  }
 }