Explain how to associate RequestFinishedInfo with original request

components/cronet/android/api/src/org/chromium/net/RequestFinishedInfo.java

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.net;
 
 import android.support.annotation.Nullable;
 
 import java.util.Collection;
 import java.util.Date;
 import java.util.concurrent.Executor;
 
 /**
  * Information about a finished request. Passed to {@link RequestFinishedInfo.Listener}.
  *
+ * To associate the data with the original request, use
+ * {@link ExperimentalUrlRequest.Builder#addRequestAnnotation} or
+ * {@link ExperimentalBidirectionalStream.Builder#addRequestAnnotation} to add a unique identifier
+ * when creating the request, and call {@link #getAnnotations} when the {@link RequestFinishedInfo}
+ * is received to retrieve the identifier.
+ *
  * {@hide} as it's a prototype.
  */
 public abstract class RequestFinishedInfo {
     /**
      * Listens for finished requests for the purpose of collecting metrics.
      *
      * {@hide} as it's a prototype.
      */
     public abstract static class Listener {
         private final Executor mExecutor;
@@ skipping 224 matching lines @@
      * Reason value indicating that the request failed or returned an error. Returned from
      * {@link #getFinishedReason}.
      */
     public static final int FAILED = 1;
     /**
      * Reason value indicating that the request was canceled. Returned from
      * {@link #getFinishedReason}.
      */
     public static final int CANCELED = 2;
 
-
-    /** Returns the request's original URL. */
+    /**
+     * Returns the request's original URL.
+     *
+     * @return the request's original URL
+     */
     public abstract String getUrl();
 
-    /** Returns the objects that the caller has supplied when initiating the request. */
+    /**
+     * Returns the objects that the caller has supplied when initiating the request, using
+     * {@link ExperimentalUrlRequest.Builder#addRequestAnnotation} or
+     * {@link ExperimentalBidirectionalStream.Builder#addRequestAnnotation}.
+     * Annotations can be used to associate a {@link RequestFinishedInfo} with the original request
+     * or type of request.
+     *
+     * @return annotations supplied when creating the request
+     */
     public abstract Collection<Object> getAnnotations();
 
     // TODO(klm): Collect and return a chain of Metrics objects for redirect responses.
     // TODO(mgersh): Update this javadoc when new metrics are fully implemented
     /**
      * Returns metrics collected for this request.
      *
      * <p>The reported times and bytes account for all redirects, i.e.
      * the TTFB is from the start of the original request to the ultimate response headers,
      * the TTLB is from the start of the original request to the end of the ultimate response,
@@ skipping 20 matching lines @@
 
     /**
      * If the request failed, returns the same {@link CronetException} provided to
      * {@link UrlRequest.Callback#onFailed}.
      *
      * @return the request's {@link CronetException}, if the request failed
      */
     @Nullable
     public abstract CronetException getException();
 }