Add a distribution JAR for WebRTC Android SDK.

webrtc/sdk/android/BUILD.gn

Index: webrtc/sdk/android/BUILD.gn
diff --git a/webrtc/sdk/android/BUILD.gn b/webrtc/sdk/android/BUILD.gn
index edd33607b2ccd0442042d63499ba58fa59f7efa0..48aaf6e2f76eaeef19a7395ead39e07a93a712d4 100644
--- a/webrtc/sdk/android/BUILD.gn
+++ b/webrtc/sdk/android/BUILD.gn
@@ -184,6 +184,13 @@ android_library("libjingle_peerconnection_metrics_default_java") {
   ]
 }
 
+dist_jar("libwebrtc") {
+  deps = [
+    ":libjingle_peerconnection_metrics_default_java",
+  ]
+  output_jar_path = "$target_out_dir/libwebrtc.jar"
+}
+
 if (rtc_include_tests) {
   instrumentation_test_apk("libjingle_peerconnection_android_unittest") {
     apk_name = "libjingle_peerconnection_android_unittest"