Fix #1771 and probably others (#2286)

This is *super* subtle, and IMHO Chrome did exactly the wrong thing
here.

test-utils/domMock.js

@@ -87,6 +87,13 @@ module.exports = function(options) {
 		var index = this.childNodes.indexOf(child)
 		if (index > -1) {
 			this.childNodes.splice(index, 1)
+			// Yes, *this* is the behavior Chrome has and what FF is considering in
+			// https://bugzilla.mozilla.org/show_bug.cgi?id=559561
+			if (activeElement === child) {
+				var blur = $window.document.createEvent()
+				blur.initEvent("blur")
+				child.dispatchEvent(blur)
+			}
 			child.parentNode = null
 		}
 		else throw new TypeError("Failed to execute 'removeChild'")

test-utils/tests/test-domMock.js

@@ -208,6 +208,19 @@ o.spec("domMock", function() {
 			try {parent.removeChild(child)}
 			catch (e) {done()}
 		})
+		o("invokes blur on child if focused", function() {
+			var parent = $document.createElement("div")
+			var child = $document.createElement("a")
+			var spy = o.spy()
+			parent.appendChild(child)
+			child.addEventListener("blur", spy, false)
+			child.focus()
+			parent.removeChild(child)
+
+			o(spy.callCount).equals(1)
+			o(spy.args[0].type).equals("blur")
+			o(spy.args[0].target).equals(child)
+		})
 	})
 
 	o.spec("insertBefore", function() {