Addressed code review comments

Author: ajaybhargavb

src/Microsoft.AspNet.Razor/Parser/CSharpCodeParser.cs

@@ -228,7 +228,7 @@ private void AfterTransition()
                                 {
                                     Context.OnError(
                                         CurrentLocation,
-                                        RazorResources.ParseError_HelperDirectiveNotAvailable,
+                                        RazorResources.FormatParseError_HelperDirectiveNotAvailable(SyntaxConstants.CSharp.HelperKeyword),
                                         CurrentSymbol.Content.Length);
                                 }
 

src/Microsoft.AspNet.Razor/Parser/SyntaxConstants.cs

@@ -27,6 +27,8 @@ public static class CSharp
             public static readonly string ElseIfKeyword = "else if";
             public static readonly string NamespaceKeyword = "namespace";
             public static readonly string ClassKeyword = "class";
+
+            // Not supported. Only used for error cases.
             public static readonly string HelperKeyword = "helper";
         }
     }

src/Microsoft.AspNet.Razor/Properties/RazorResources.Designer.cs

@@ -426,6 +426,6 @@ Instead, wrap the contents of the block in "{{}}":
     <value>The &amp;lt;{0}&amp;gt; tag is not allowed by parent &amp;lt;{1}&amp;gt; tag helper. Only child tag helper(s) targeting tag name(s) '{2}' are allowed.</value>
   </data>
   <data name="ParseError_HelperDirectiveNotAvailable" xml:space="preserve">
-    <value>The @helper directive is not available in Razor 4.</value>
+    <value>The {0} directive is no longer supported.</value>
   </data>
 </root>

src/Microsoft.AspNet.Razor/RazorResources.resx

@@ -30,16 +30,16 @@ public void ParseBlockHandlesQuotesAfterTransition()
         [Fact]
         public void ParseBlockWithHelperDirectiveProducesError()
         {
-            ParseBlockTest("@helper { }",
-                           new ExpressionBlock(
-                               Factory.CodeTransition(),
-                               Factory.Code("helper")
-                                   .AsImplicitExpression(KeywordSet)
-                                   .Accepts(AcceptedCharacters.NonWhiteSpace)),
-                           new RazorError(
-                               RazorResources.ParseError_HelperDirectiveNotAvailable,
-                               new SourceLocation(1, 0, 1),
-                               length: 6));
+            ParseBlockTest("@helper fooHelper { }",
+                new ExpressionBlock(
+                    Factory.CodeTransition(),
+                    Factory.Code("helper")
+                        .AsImplicitExpression(KeywordSet)
+                        .Accepts(AcceptedCharacters.NonWhiteSpace)),
+                new RazorError(
+                    RazorResources.FormatParseError_HelperDirectiveNotAvailable(SyntaxConstants.CSharp.HelperKeyword),
+                    new SourceLocation(1, 0, 1),
+                    length: 6));
         }
 
         [Fact]