Don't kill Chrome Apps that make XHRs from guests.

chrome/test/data/extensions/platform_apps/web_view/content_script_fetch/content_script.js

Index: chrome/test/data/extensions/platform_apps/web_view/content_script_fetch/content_script.js
diff --git a/chrome/test/data/extensions/platform_apps/web_view/content_script_fetch/content_script.js b/chrome/test/data/extensions/platform_apps/web_view/content_script_fetch/content_script.js
new file mode 100644
index 0000000000000000000000000000000000000000..3ec97f41b215d8744330169a7c8daaadbb828584
--- /dev/null
+++ b/chrome/test/data/extensions/platform_apps/web_view/content_script_fetch/content_script.js
@@ -0,0 +1,34 @@
+// Copyright 2017 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.
+
+var embedder = null;
+
+function reportResult(result) {
+  window.console.log('Reporting ' + result + ' to embedder.');
+  var msg = ['fetch-' + result];
+  embedder.postMessage(JSON.stringify(msg), '*');
+}
+
+window.addEventListener('message', function(e) {
+  window.console.log('Content script received message.')
+  embedder = e.source;
+  var data = JSON.parse(e.data);
+  switch (data[0]) {
+    case 'start-fetch': {

[Devlin, 2017/04/06 18:32:13]

A switch for a single case is a little weird.  Can this just be an if?  And
should we fail if it's anything else, or are other messages expected?

[Charlie Reis, 2017/04/06 19:21:59]

Done.

+      fetch('http://127.0.0.1:' + location.port + '/extensions/xhr.txt')
+          .then((result) => result.text())
+          .then((text) => {
+            reportResult(
+                (text == 'File to request via XHR.\n') ? 'success' : 'failure');
+          })
+          .catch(err => {
+            console.log('Error: ' + err);
+            reportResult('failure');
+          });
+      break;
+    }
+  }
+});
+
+window.console.log('Script has been successfully injected.');