fix($interval): throw when trying to cancel non-$interval promise

Previously, calling `$interval.cancel()` with a promise that was not
generated by a call to `$interval()` would do nothing. This could, for
example, happen when calling `.then()`/`.catch()` on the returned
promise, which creates a new promise, and passing that to
`$interval.cancel()`.
With this commit, `$interval.cancel()` will throw an error if called
with a non-$interval promise, thus surfacing errors that would otherwise
go unnoticed.

Related to #16424.

BREAKING CHNAGE:

`$interval.cancel()` will throw an error if called with a promise that
was not generated by `$interval()`. Previously, it would silently do
nothing.

Before:
```js
var promise = $interval(doSomething, 1000, 5).then(doSomethingElse);
$interval.cancel(promise);  // No error; interval NOT canceled.
```

After:
```js
var promise = $interval(doSomething, 1000, 5).then(doSomethingElse);
$interval.cancel(promise);  // Throws error.
```

Correct usage:
```js
var promise = $interval(doSomething, 1000, 5);
var newPromise = promise.then(doSomethingElse);
$interval.cancel(promise);  // Interval canceled.
```

Closes #16476

docs/content/error/$interval/badprom.ngdoc

@@ -0,0 +1,25 @@
+@ngdoc error
+@name $interval:badprom
+@fullName Non-$interval promise
+@description
+
+This error occurs when calling {@link ng.$interval#cancel $interval.cancel()} with a promise that
+was not generated by the {@link ng.$interval $interval} service. This can, for example, happen when
+calling {@link ng.$q#the-promise-api then()/catch()} on the returned promise, which creates a new
+promise, and pass that new promise to {@link ng.$interval#cancel $interval.cancel()}.
+
+Example of incorrect usage that leads to this error:
+
+```js
+var promise = $interval(doSomething, 1000, 5).then(doSomethingElse);
+$interval.cancel(promise);
+```
+
+To fix the example above, keep a reference to the promise returned by
+{@link ng.$interval $interval()} and pass that to {@link ng.$interval#cancel $interval.cancel()}:
+
+```js
+var promise = $interval(doSomething, 1000, 5);
+var newPromise = promise.then(doSomethingElse);
+$interval.cancel(promise);
+```

src/ng/interval.js

@@ -1,5 +1,7 @@
 'use strict';
 
+var $intervalMinErr = minErr('$interval');
+
 /** @this */
 function $IntervalProvider() {
   this.$get = ['$rootScope', '$window', '$q', '$$q', '$browser',
@@ -188,15 +190,25 @@ function $IntervalProvider() {
      * @returns {boolean} Returns `true` if the task was successfully canceled.
      */
     interval.cancel = function(promise) {
-      if (promise && promise.$$intervalId in intervals) {
-        // Interval cancels should not report as unhandled promise.
-        markQExceptionHandled(intervals[promise.$$intervalId].promise);
-        intervals[promise.$$intervalId].reject('canceled');
-        $window.clearInterval(promise.$$intervalId);
-        delete intervals[promise.$$intervalId];
-        return true;
+      if (!promise) return false;
+
+      if (!promise.hasOwnProperty('$$intervalId')) {
+        throw $intervalMinErr('badprom',
+            '`$interval.cancel()` called with a promise that was not generated by `$interval()`.');
       }
-      return false;
+
+      if (!intervals.hasOwnProperty(promise.$$intervalId)) return false;
+
+      var id = promise.$$intervalId;
+      var deferred = intervals[id];
+
+      // Interval cancels should not report an unhandled promise.
+      markQExceptionHandled(deferred.promise);
+      deferred.reject('canceled');
+      $window.clearInterval(id);
+      delete intervals[id];
+
+      return true;
     };
 
     return interval;

test/ng/intervalSpec.js

@@ -335,12 +335,17 @@ describe('$interval', function() {
     }));
 
 
-    it('should not throw a runtime exception when given an undefined promise',
-        inject(function($interval) {
+    it('should not throw an error when given an undefined promise', inject(function($interval) {
       expect($interval.cancel()).toBe(false);
     }));
 
 
+    it('should throw an error when given a non-$interval promise', inject(function($interval) {
+      var promise = $interval(noop).then(noop);
+      expect(function() { $interval.cancel(promise); }).toThrowMinErr('$interval', 'badprom');
+    }));
+
+
     it('should not trigger digest when cancelled', inject(function($interval, $rootScope, $browser) {
       var watchSpy = jasmine.createSpy('watchSpy');
       $rootScope.$watch(watchSpy);