Add HttpUrlConnection backed implementation of CronetEngine.

components/cronet/android/test/javatests/src/org/chromium/net/CronetUrlTest.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.content.Context;
 import android.test.suitebuilder.annotation.SmallTest;
 
 import org.chromium.base.PathUtils;
@@ skipping 36 matching lines @@
         CronetTestFramework testFramework =
                 startCronetTestFrameworkWithUrlAndCommandLineArgs(URL, commandLineArgs);
 
         // Make sure that the URL is set as expected.
         assertEquals(URL, testFramework.getUrl());
         assertEquals(200, testFramework.getHttpStatusCode());
     }
 
     @SmallTest
     @Feature({"Cronet"})
+    @OnlyRunNativeCronet

[pauljensen, 2015/12/08 19:49:53]

can we add comment saying "no NetLog from HttpURLConnection"

[Charles, 2015/12/11 16:45:40]

Done.

     public void testNetLog() throws Exception {
         Context context = getContext();
         File directory = new File(PathUtils.getDataDirectory(context));
         File file = File.createTempFile("cronet", "json", directory);
         HttpUrlRequestFactory factory = HttpUrlRequestFactory.createFactory(
                 context,
                 new UrlRequestContextConfig().setLibraryName("cronet_tests"));
         // Start NetLog immediately after the request context is created to make
         // sure that the call won't crash the app even when the native request
         // context is not fully initialized. See crbug.com/470196.
@@ skipping 91 matching lines @@
                 URL, HttpUrlRequest.REQUEST_PRIORITY_MEDIUM, headers, listener);
         request.setHttpMethod("HEAD");
         request.start();
         listener.blockForComplete();
         assertEquals(200, listener.mHttpStatusCode);
         // HEAD requests do not get any response data and Content-Length must be
         // ignored.
         assertEquals(0, listener.mResponseAsBytes.length);
     }
 }