Fix xhr abort test.

Need to be more creative about ensuring that onreadystatechange is
called, but that the test conditions execute after that the function
(that does nothing...) is called.

request/tests/test-request.js

@@ -397,13 +397,30 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: JSON.stringify({a: 1})}
 				}
 			})
+
 			var failed = false
-			xhr({method: "GET", url: "/item", config: function (xhr) { setTimeout(function() { xhr.abort() }, 0) }}).catch(function() {
-				failed = true
-			}).then(function() {
+			var resolved = false
+			function handleAbort(xhr) {
+				var onreadystatechange = xhr.onreadystatechange // probably not set yet
+				var testonreadystatechange = function() {
+					onreadystatechange.call(xhr)
+					setTimeout(function() { // allow promises to (not) resolve first
 						o(failed).equals(false)
-			}).then(function() {
+						o(resolved).equals(false)
 						done()
+					}, 0)
+				}
+				Object.defineProperty(xhr, 'onreadystatechange', {
+					set: function(val) { onreadystatechange = val }
+					, get: function() { return testonreadystatechange }
+				})
+				xhr.abort()
+			}
+			xhr({method: "GET", url: "/item", config: handleAbort}).catch(function() {
+				failed = true
+			})
+			.then(function() {
+				resolved = true
 			})
 		})
 		o("doesn't fail on file:// status 0", function(done) {