perf($compile,ngModel,form): avoid invoking $interpolate for empty/falsy values

Author: jbedard

src/ng/compile.js

@@ -1387,7 +1387,9 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
                   attrs[nName] = true; // presence means true
                 }
             }
-            addAttrInterpolateDirective(node, directives, value, nName, isNgAttr);
+            if (value) {
+              addAttrInterpolateDirective(node, directives, value, nName, isNgAttr);
+            }
             addDirective(directives, nName, 'A', maxPriority, ignoreDirective, attrStartName,
                           attrEndName);
           }
@@ -1405,7 +1407,9 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
           }
           break;
         case NODE_TYPE_TEXT: /* Text Node */
-          addTextInterpolateDirective(directives, node.nodeValue);
+          if (value = node.nodeValue) {
+            addTextInterpolateDirective(directives, value);
+          }
           break;
         case NODE_TYPE_COMMENT: /* Comment */
           try {

src/ng/directive/form.js

@@ -70,7 +70,7 @@ function FormController(element, attrs, $scope, $animate, $interpolate) {
   form.$error = {};
   form.$$success = {};
   form.$pending = undefined;
-  form.$name = $interpolate(attrs.name || attrs.ngForm || '')($scope);
+  form.$name = (attrs.name || attrs.ngForm) && $interpolate(attrs.name || attrs.ngForm)($scope) || '';
   form.$dirty = false;
   form.$pristine = true;
   form.$valid = true;

src/ng/directive/input.js

@@ -1712,7 +1712,7 @@ var NgModelController = ['$scope', '$exceptionHandler', '$attrs', '$element', '$
   this.$error = {}; // keep invalid keys here
   this.$$success = {}; // keep valid keys here
   this.$pending = undefined; // keep pending keys here
-  this.$name = $interpolate($attr.name || '', false)($scope);
+  this.$name = $attr.name && $interpolate($attr.name)($scope) || '';
 
 
   var parsedNgModel = $parse($attr.ngModel),