Correctly remove spies of window.onerror on IE

spec/html/SpyRegistryHtmlSpec.js

@@ -0,0 +1,34 @@
+describe('Spy Registry browser-specific behavior', function() {
+  it('can spy on and unspy window.onerror', function() {
+    requireWriteableOnerror();
+
+    var spies = [],
+      spyRegistry = new jasmineUnderTest.SpyRegistry({
+		  currentSpies: function() { return spies; },
+		  global: window
+		  }),
+      originalHandler = window.onerror;
+
+    try {
+      spyRegistry.spyOn(window, 'onerror');
+      spyRegistry.clearSpies();
+      expect(window.onerror).toBe(originalHandler);
+    } finally {
+      window.onerror = originalHandler;
+    }
+  });
+
+  function requireWriteableOnerror() {
+    var descriptor;
+
+    try {
+      descriptor = Object.getOwnPropertyDescriptor(window, 'onerror');
+    } catch(e) {
+      // IE 8 doesn't support `definePropery` on non-DOM nodes
+    }
+
+    if (descriptor && !(descriptor.writable || descriptor.set)) {
+      pending('Browser declares window.onerror to be readonly');
+    }
+  }
+});