Fix for issue 3401: Implement casts in Analyzer

compiler/java/com/google/dart/compiler/parser/DartParser.java

Index: compiler/java/com/google/dart/compiler/parser/DartParser.java
===================================================================
--- compiler/java/com/google/dart/compiler/parser/DartParser.java	(revision 8338)
+++ compiler/java/com/google/dart/compiler/parser/DartParser.java	(working copy)
@@ -1889,6 +1889,10 @@
           } else {
             right = done(new DartTypeExpression(parseTypeAnnotation()));
           }
+        } else if (token == Token.AS) {
+          beginCastExpression();
+          beginTypeExpression();
+          right = done(new DartTypeExpression(parseTypeAnnotation()));
         } else {
           right = parseBinaryExpression(level + 1);
         }
@@ -1898,7 +1902,8 @@
 
         lastResult = right;
         result = doneWithoutConsuming(new DartBinaryExpression(token, result, right));
-        if ((token == Token.IS)
+        if (token == Token.IS
+            || token == Token.AS
             || token.isRelationalOperator()
             || token.isEqualityOperator()) {
           // The operations cannot be chained.