fix(ngEventDirectives): parse expression only once during compile phase.

Author: tbosch

src/ng/directive/ngEventDirs.js

@@ -41,13 +41,17 @@ forEach(
   function(name) {
     var directiveName = directiveNormalize('ng-' + name);
     ngEventDirectives[directiveName] = ['$parse', function($parse) {
-      return function(scope, element, attr) {
-        var fn = $parse(attr[directiveName]);
-        element.on(lowercase(name), function(event) {
-          scope.$apply(function() {
-            fn(scope, {$event:event});
-          });
-        });
+      return {
+        compile: function($element, attr) {
+          var fn = $parse(attr[directiveName]);
+          return function(scope, element, attr) {
+            element.on(lowercase(name), function(event) {
+              scope.$apply(function() {
+                fn(scope, {$event:event});
+              });
+            });
+          };
+        }
       };
     }];
   }