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diff --git a/tools/addon-sdk-1.7/packages/api-utils/lib/xhr.js b/tools/addon-sdk-1.7/packages/api-utils/lib/xhr.js
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {Cc,Ci} = require("chrome");
+const memory = require('api-utils/memory');
+
+// ## Implementation Notes ##
+// 
+// Making `XMLHttpRequest` objects available to Jetpack code involves a
+// few key principles universal to all low-level module implementations:
+//
+// * **Unloadability**. A Jetpack-based extension using this module can be 
+//   asked to unload itself at any time, e.g. because the user decides to
+//   uninstall or disable the extension. This means we need to keep track of
+//   all in-progress reqests and abort them on unload.
+//
+// * **Developer-Ergonomic Tracebacks**. Whenever an exception is raised
+//   by a Jetpack-based extension, we want it to be logged in a
+//   place that is specific to that extension--so that a developer
+//   can distinguish it from an error on a web page or in another
+//   extension, for instance. We also want it to be logged with a
+//   full stack traceback, which the Mozilla platform doesn't usually
+//   do.
+//
+//   Because of this, we don't actually want to give the Mozilla
+//   platform's "real" XHR implementation to clients, but instead provide
+//   a simple wrapper that trivially delegates to the implementation in
+//   all cases except where callbacks are involved: whenever Mozilla
+//   platform code calls into the extension, such as during the XHR's
+//   `onreadystatechange` callback, we want to wrap the client's callback
+//   in a try-catch clause that traps any exceptions raised by the
+//   callback and logs them via console.exception() instead of allowing
+//   them to propagate back into Mozilla platform code.
+
+// This is a private list of all active requests, so we know what to
+// abort if we're asked to unload.
+var requests = [];
+
+// Events on XHRs that we should listen for, so we know when to remove
+// a request from our private list.
+const TERMINATE_EVENTS = ["load", "error", "abort"];
+
+// Read-only properties of XMLHttpRequest objects that we want to
+// directly delegate to.
+const READ_ONLY_PROPS = ["readyState", "responseText", "responseXML",
+                         "status", "statusText"];
+
+// Methods of XMLHttpRequest that we want to directly delegate to.
+const DELEGATED_METHODS = ["abort", "getAllResponseHeaders",
+                           "getResponseHeader", "overrideMimeType",
+                           "send", "sendAsBinary", "setRequestHeader",
+                           "open"];
+
+var getRequestCount = exports.getRequestCount = function getRequestCount() {
+  return requests.length;
+};
+
+var XMLHttpRequest = exports.XMLHttpRequest = function XMLHttpRequest() {
+  var req = Cc["@mozilla.org/xmlextras/xmlhttprequest;1"]
+            .createInstance(Ci.nsIXMLHttpRequest);
+  // For the sake of simplicity, don't tie this request to any UI.
+  req.mozBackgroundRequest = true;
+
+  memory.track(req, "XMLHttpRequest");
+
+  this._req = req;
+  this._orsc = null;
+
+  requests.push(this);
+
+  var self = this;
+
+  this._boundCleanup = function _boundCleanup() {
+    self._cleanup();
+  };
+
+  TERMINATE_EVENTS.forEach(
+    function(name) {
+      self._req.addEventListener(name, self._boundCleanup, false);
+    });
+};
+
+XMLHttpRequest.prototype = {
+  _cleanup: function _cleanup() {
+    this.onreadystatechange = null;
+    var index = requests.indexOf(this);
+    if (index != -1) {
+      var self = this;
+      TERMINATE_EVENTS.forEach(
+        function(name) {
+          self._req.removeEventListener(name, self._boundCleanup, false);
+        });
+      requests.splice(index, 1);
+    }
+  },
+  _unload: function _unload() {
+    this._req.abort();
+    this._cleanup();
+  },
+  addEventListener: function addEventListener() {
+    throw new Error("not implemented");
+  },
+  removeEventListener: function removeEventListener() {
+    throw new Error("not implemented");
+  },
+  set upload(newValue) {
+    throw new Error("not implemented");
+  },
+  get onreadystatechange() {
+    return this._orsc;
+  },
+  set onreadystatechange(cb) {
+    this._orsc = cb;
+    if (cb) {
+      var self = this;
+      this._req.onreadystatechange = function() {
+        try {
+          self._orsc.apply(self, arguments);
+        } catch (e) {
+          console.exception(e);
+        }
+      };
+    } else
+      this._req.onreadystatechange = null;
+  }
+};
+
+READ_ONLY_PROPS.forEach(
+   function(name) {
+     XMLHttpRequest.prototype.__defineGetter__(
+       name,
+       function() {
+         return this._req[name];
+       });
+   });
+
+DELEGATED_METHODS.forEach(
+  function(name) {
+    XMLHttpRequest.prototype[name] = function() {
+      return this._req[name].apply(this._req, arguments);
+    };
+  });
+
+require("./unload").when(
+  function() {
+    requests.slice().forEach(function(request) { request._unload(); });
+  });