fix($injector): do not use inherited $inject

Ensure that a function has its own $inject property, and not an inherited
property, when annotating. This ensures that derived functions / classes do not
get the dependencies of their super class.

Fixes #15536

Author: ChrisMondok

src/auto/injector.js

@@ -100,7 +100,8 @@ function annotate(fn, strictDi, name) {
       last;
 
   if (typeof fn === 'function') {
-    if (!($inject = fn.$inject)) {
+    $inject = fn.hasOwnProperty('$inject') ? fn.$inject : undefined;
+    if (!$inject) {
       $inject = [];
       if (fn.length) {
         if (strictDi) {

test/auto/injectorSpec.js

@@ -191,6 +191,15 @@ describe('injector', function() {
     });
 
 
+    it('should not use inherited $inject', function() {
+      function base() {}
+      base.$inject = ['a'];
+      function derived(b) {};
+      Object.setPrototypeOf(derived, base);
+      expect(annotate(derived)).toEqual(['b']);
+    });
+
+
     it('should create $inject', function() {
       var extraParams = angular.noop;
       /* eslint-disable space-before-function-paren */