fix(jqLite): allow triggerHandler() to accept custom event

In some scenarios you want to be able to specify properties on the event
that is passed to the event handler. JQuery does this by overloading the
first parameter (`eventName`). If it is an object with a `type` property
then we assume that it must be a custom event.

In this case the custom event must provide the `type` property which is
the name of the event to be triggered.  `triggerHandler` will continue to
provide dummy default functions for `preventDefault()`, `isDefaultPrevented()`
and `stopPropagation()` but you may override these with your own versions
in your custom object if you wish.

Closes angular#8469

Author: petebacondarwin

src/jqLite.js

@@ -947,32 +947,37 @@ forEach({
 
   clone: jqLiteClone,
 
-  triggerHandler: function(element, eventName, eventData) {
-
-    var event = {
-      preventDefault: function() {
-        this.defaultPrevented = true;
-      },
-      isDefaultPrevented: function() {
-        return this.defaultPrevented === true;
-      },
-      stopPropagation: noop
-    };
+  triggerHandler: function(element, event, eventData) {
 
-    if ( eventName.type ) {
-      extend(event, eventName);
-      eventName = event.type;
-    }
+    var dummyEvent, eventFnsCopy, handlerArgs;
+    var eventName = event.type || event;
+    var eventFns = (jqLiteExpandoStore(element, 'events') || {})[eventName];
 
-    var handlerArgs = [event].concat(eventData || []);
+    if (eventFns) {
 
-    // Copy event handlers in case event handlers array is modified during execution.
-    var eventFns = (jqLiteExpandoStore(element, 'events') || {})[eventName],
-        eventFnsCopy = shallowCopy(eventFns || []);
+      // Create a dummy event to pass to the handlers
+      dummyEvent = {
+        preventDefault: function() { this.defaultPrevented = true; },
+        isDefaultPrevented: function() { return this.defaultPrevented === true; },
+        stopPropagation: noop,
+        type: eventName,
+        target: element
+      };
 
-    forEach(eventFnsCopy, function(fn) {
-      fn.apply(element, handlerArgs);
-    });
+      // If a custom event was provided then extend our dummy event with it
+      if (event.type) {
+        dummyEvent = extend(dummyEvent, event);
+      }
+
+      // Copy event handlers in case event handlers array is modified during execution.
+      eventFnsCopy = shallowCopy(eventFns);
+      handlerArgs = eventData ? [dummyEvent].concat(eventData) : [dummyEvent];
+
+      forEach(eventFnsCopy, function(fn) {
+        fn.apply(element, handlerArgs);
+      });
+
+    }
   }
 }, function(fn, name){
   /**