perf($compile): use createMap() for directive bindings to allow fast forEach

Closes #12529

src/ng/compile.js

@@ -873,7 +873,7 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
   function parseIsolateBindings(scope, directiveName, isController) {
     var LOCAL_REGEXP = /^\s*([@&<]|=(\*?))(\??)\s*(\w*)\s*$/;
 
-    var bindings = {};
+    var bindings = createMap();
 
     forEach(scope, function(definition, scopeName) {
       if (definition in bindingCache) {