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 #5420
Closes #14686

src/ngMock/angular-mocks.js

@@ -106,19 +106,29 @@ angular.mock.$Browser = function() {
    * @param {number=} number of milliseconds to flush. See {@link #defer.now}
    */
   self.defer.flush = function(delay) {
+    var nextTime;
+
     if (angular.isDefined(delay)) {
-      self.defer.now += delay;
+      // A delay was passed so compute the next time
+      nextTime = self.defer.now + delay;
     } else {
       if (self.deferredFns.length) {
-        self.defer.now = self.deferredFns[self.deferredFns.length - 1].time;
+        // 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');
       }
     }
 
-    while (self.deferredFns.length && self.deferredFns[0].time <= self.defer.now) {
+    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 = '/';

test/ngMock/angular-mocksSpec.js

@@ -296,8 +296,10 @@ describe('ngMock', function() {
       expect(counter).toBe(1);
 
       $interval.flush(1000);
-
       expect(counter).toBe(2);
+
+      $interval.flush(2000);
+      expect(counter).toBe(4);
     }));
 
 
@@ -692,6 +694,30 @@ describe('ngMock', function() {
       $timeout.flush(123);
       expect(count).toBe(2);
     }));
+
+    it('should resolve timeout functions following the timeline', inject(function($timeout) {
+      var count1 = 0, count2 = 0;
+      var iterate1 = function() {
+        count1++;
+        $timeout(iterate1, 100);
+      };
+      var iterate2 = function() {
+        count2++;
+        $timeout(iterate2, 150);
+      };
+
+      $timeout(iterate1, 100);
+      $timeout(iterate2, 150);
+      $timeout.flush(150);
+      expect(count1).toBe(1);
+      expect(count2).toBe(1);
+      $timeout.flush(50);
+      expect(count1).toBe(2);
+      expect(count2).toBe(1);
+      $timeout.flush(400);
+      expect(count1).toBe(6);
+      expect(count2).toBe(4);
+    }));
   });