fix($timeout): make $flush handle new $timeouts added in $timeout callbacks

If a $timeout handler calls $timeout itself, this new $timeout should be
added to the mock deferred queue with a "now" time based on when the original
handler was triggered.

Previously it was being added with a now time of when the `$timeout.flush`
method was originally called.

Closes angular#5420

Author: petebacondarwin

src/ngMock/angular-mocks.js

@@ -106,23 +106,29 @@ angular.mock.$Browser = function() {
    * @param {number=} number of milliseconds to flush. See {@link #defer.now}
    */
   self.defer.flush = function(delay) {
-    try {
-      if (!angular.isDefined(delay)) {
-        if (self.deferredFns.length) {
-          delay = self.deferredFns[self.deferredFns.length-1].time - self.defer.now;
-        } else {
-          throw new Error('No deferred tasks to be flushed');
-        }
-      }
+    var nextTime;
 
-      while (self.deferredFns.length && self.deferredFns[0].time <= self.defer.now + delay) {
-        delay -= (self.deferredFns[0].time - self.defer.now);
-        self.defer.now = self.deferredFns[0].time;
-        self.deferredFns.shift().fn();
+    if (angular.isDefined(delay)) {
+      // A delay was passed so compute the next time
+      nextTime = self.defer.now + delay;
+    } else {
+      if (self.deferredFns.length) {
+        // No delay was passed so set the next time so that it clears the deferred queue
+        nextTime = self.deferredFns[self.deferredFns.length - 1].time;
+      } else {
+        // No delay passed, but there are no deferred tasks so flush - indicates an error!
+        throw new Error('No deferred tasks to be flushed');
       }
-    } finally {
-      self.defer.now += delay;
     }
+
+    while (self.deferredFns.length && self.deferredFns[0].time <= nextTime) {
+      // Increment the time and call the next deferred function
+      self.defer.now = self.deferredFns[0].time;
+      self.deferredFns.shift().fn();
+    }
+
+    // Ensure that the current time is correct
+    self.defer.now = nextTime;
   };
 
   self.$$baseHref = '/';