fixup! perf(ngStyleDirective): use $watchCollection

Author: jbedard

test/ng/directive/ngStyleSpec.js

@@ -23,6 +23,21 @@ describe('ngStyle', function() {
   }));
 
 
+  it('should not deep watch objects', inject(function($rootScope, $compile) {
+    element = $compile('<div ng-style="{height: heightObj}"></div>')($rootScope);
+    $rootScope.$digest();
+    expect(parseInt(element.css('height') + 0, 10)).toEqual(0); // height could be '' or '0px'
+    $rootScope.heightObj = {toString: function() { return '40px'; }};
+    $rootScope.$digest();
+    expect(element.css('height')).toBe('40px');
+
+    element.css('height', '10px');
+    $rootScope.heightObj.otherProp = 123;
+    $rootScope.$digest();
+    expect(element.css('height')).toBe('10px');
+  }));
+
+
   it('should support binding for object literals', inject(function($rootScope, $compile) {
     element = $compile('<div ng-style="{height: heightStr}"></div>')($rootScope);
     $rootScope.$digest();