Add comment field to ExperimentalApi

core/src/main/java/io/grpc/ChannelImpl.java

@@ -255,7 +255,7 @@ public final class ChannelImpl extends Channel {
    *
    * @see ClientTransport#ping(PingCallback, Executor)
    */
-  @ExperimentalApi
+  @ExperimentalApi(comment = "https://github.com/grpc/grpc-java/issues/737")
   public void ping(final PingCallback callback, final Executor executor) {
     try {
       obtainActiveTransport().ping(callback, executor);

core/src/main/java/io/grpc/Context.java

@@ -110,7 +110,7 @@ import javax.annotation.Nullable;
  * responsibility of the application to ensure that all contexts are properly cancelled.</li>
  * </ul>
  */
-@ExperimentalApi
+@ExperimentalApi(comment = "https://github.com/grpc/grpc-java/issues/262")
 public class Context {
 
   private static final Logger LOG = Logger.getLogger(Context.class.getName());

core/src/main/java/io/grpc/ExperimentalApi.java

@@ -60,4 +60,8 @@ import java.lang.annotation.Target;
     ElementType.TYPE})
 @Documented
 public @interface ExperimentalApi {
+  /**
+   * Context information such as links to discussion thread, tracking issue etc.
+   */
+  String comment() default "";
 }