fix(cdk/testing/testbed): set defined event properties as configurable

For a couple of events, we update properties using `defineProperty`
or `defineProperties`. These by default use `configurable: false`.

This does not match the behavior of native event properties
we just overwrote. Those properties are readonly, but still
configurable. We should match that behavior so that the
synthetic events behave similar to actual event objects.

Author: devversion

src/cdk/testing/testbed/fake-events/event-objects.ts

@@ -41,7 +41,7 @@ export function createMouseEvent(type: string, clientX = 0, clientY = 0, button
 
   // `initMouseEvent` doesn't allow us to pass the `buttons` and
   // defaults it to 0 which looks like a fake event.
-  Object.defineProperty(event, 'buttons', {get: () => 1});
+  defineReadonlyEventProperty(event, 'buttons', 1);
 
   // IE won't set `defaultPrevented` on synthetic events so we need to do it manually.
   event.preventDefault = function() {
@@ -89,11 +89,9 @@ export function createTouchEvent(type: string, pageX = 0, pageY = 0) {
 
   // Most of the browsers don't have a "initTouchEvent" method that can be used to define
   // the touch details.
-  Object.defineProperties(event, {
-    touches: {value: [touchDetails]},
-    targetTouches: {value: [touchDetails]},
-    changedTouches: {value: [touchDetails]}
-  });
+  defineReadonlyEventProperty(event, 'touches', [touchDetails]);
+  defineReadonlyEventProperty(event, 'targetTouches', [touchDetails]);
+  defineReadonlyEventProperty(event, 'changedTouches', [touchDetails]);
 
   return event;
 }
@@ -145,15 +143,13 @@ export function createKeyboardEvent(type: string, keyCode: number = 0, key: stri
 
   // Webkit Browsers don't set the keyCode when calling the init function.
   // See related bug https://bugs.webkit.org/show_bug.cgi?id=16735
-  Object.defineProperties(event, {
-    keyCode: { get: () => keyCode },
-    key: { get: () => key },
-    target: { get: () => target },
-    ctrlKey: { get: () => !!modifiers.control },
-    altKey: { get: () => !!modifiers.alt },
-    shiftKey: { get: () => !!modifiers.shift },
-    metaKey: { get: () => !!modifiers.meta }
-  });
+  defineReadonlyEventProperty(event, 'keyCode', keyCode);
+  defineReadonlyEventProperty(event, 'key', key);
+  defineReadonlyEventProperty(event, 'target', target);
+  defineReadonlyEventProperty(event, 'ctrlKey', !!modifiers.control);
+  defineReadonlyEventProperty(event, 'altKey', !!modifiers.alt);
+  defineReadonlyEventProperty(event, 'shiftKey', !!modifiers.shift);
+  defineReadonlyEventProperty(event, 'metaKey', !!modifiers.meta);
 
   // IE won't set `defaultPrevented` on synthetic events so we need to do it manually.
   event.preventDefault = function() {