[Cronet] Implement methods to get response headers in HttpURLConnection.

components/cronet/android/java/src/org/chromium/net/CronetUrlRequest.java

 // Copyright 2014 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.util.Log;
 import android.util.Pair;
 
 import org.chromium.base.CalledByNative;
 import org.chromium.base.JNINamespace;
 
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.Collections;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.TreeMap;
 import java.util.concurrent.Executor;
 
 /**
  * UrlRequest using Chromium HTTP stack implementation. Could be accessed from
  * any thread on Executor. Cancel can be done from any thread.
  * All @CallByNative methods are called on native network thread
  * and post tasks with listener calls onto Executor. Upon return from listener
  * callback native request adapter is called on executive thread and posts
  * native tasks to native network thread. Because Cancel could be called from
  * any thread it is protected by mUrlRequestAdapterLock.
@@ skipping 81 matching lines @@
         }
     }
 
     static final class NativeResponseInfo implements ResponseInfo {
         private final String[] mResponseInfoUrlChain;
         private final int mHttpStatusCode;
         private final String mHttpStatusText;
         private final HeadersList mAllHeaders = new HeadersList();
         private final boolean mWasCached;
         private final String mNegotiatedProtocol;
+        private Map<String, List<String>> mResponseHeaders;
+        private List<Pair<String, String>> mUnmodifiableAllHeaders;
 
         NativeResponseInfo(String[] urlChain, int httpStatusCode,
                 String httpStatusText, boolean wasCached,
                 String negotiatedProtocol) {
             mResponseInfoUrlChain = urlChain;
             mHttpStatusCode = httpStatusCode;
             mHttpStatusText = httpStatusText;
             mWasCached = wasCached;
             mNegotiatedProtocol = negotiatedProtocol;
         }
@@ skipping 13 matching lines @@
             return mHttpStatusCode;
         }
 
         @Override
         public String getHttpStatusText() {
             return mHttpStatusText;
         }
 
         @Override
         public List<Pair<String, String>> getAllHeadersAsList() {
-            return Collections.unmodifiableList(mAllHeaders);
+            if (mUnmodifiableAllHeaders == null) {
+                mUnmodifiableAllHeaders =
+                        Collections.unmodifiableList(mAllHeaders);
+            }
+            return mUnmodifiableAllHeaders;

[mef, 2015/01/30 16:22:51]

Do I understand correctly that the reason to return unmodifiableList is to
prevent embedder from inadvertently changing it?

[xunjieli, 2015/01/30 18:22:58]

Yes, this seems to be an requirement for HttpURLConnection methods, so I thought
it'd be a good practice for the underlying ResponseInfo as well.

         }
 
         @Override
         public Map<String, List<String>> getAllHeaders() {
-            Map<String, List<String>> map = new HashMap<String, List<String>>();
+            if (mResponseHeaders != null) {
+                return mResponseHeaders;
+            }
+            Map<String, List<String>> map = new TreeMap<String, List<String>>(
+                    String.CASE_INSENSITIVE_ORDER);
             for (Pair<String, String> entry : mAllHeaders) {
+                List<String> values = new ArrayList<String>();
                 if (map.containsKey(entry.first)) {
-                    map.get(entry.first).add(entry.second);
-                } else {
-                    List<String> values = new ArrayList<String>();
-                    values.add(entry.second);
-                    map.put(entry.first, values);
+                    values.addAll(map.get(entry.first));
                 }
+                values.add(entry.second);
+                map.put(entry.first, Collections.unmodifiableList(values));
             }
-            return Collections.unmodifiableMap(map);
+            mResponseHeaders = Collections.unmodifiableMap(map);
+            return mResponseHeaders;
         }
 
         @Override
         public boolean wasCached() {
             return mWasCached;
         }
 
         @Override
         public String getNegotiatedProtocol() {
             return mNegotiatedProtocol;
@@ skipping 425 matching lines @@
             HeadersList headers);
 
     private native String nativeGetNegotiatedProtocol(long urlRequestAdapter);
 
     private native String nativeGetHttpStatusText(long urlRequestAdapter);
 
     private native boolean nativeGetWasCached(long urlRequestAdapter);
 
     private native long nativeGetTotalReceivedBytes(long urlRequestAdapter);
 }