fix(onProperty): user quoted access for __Zone_ignore_on_properties (#1134)

Avoid closure renaming while accessing the global symbol.

Author: vikerman

lib/browser/property-descriptor.ts

@@ -272,7 +272,7 @@ export function propertyDescriptorPatch(api: _ZonePrivate, _global: any) {
 
 constsupportsWebSocket=typeofWebSocket!=='undefined';
 if(canPatchViaPropertyDescriptor()){
-constignoreProperties: IgnoreProperty[]=_global.__Zone_ignore_on_properties;
+constignoreProperties: IgnoreProperty[]=_global['__Zone_ignore_on_properties'];
 // for browsers that we can patch the descriptor: Chrome & Firefox
 if(isBrowser){
 constinternalWindow: any=window;