Fix a couple cast errors

src/ast.h

Index: src/ast.h
diff --git a/src/ast.h b/src/ast.h
index ed447e343af26c4e5a91dcc5cf91237d9a70c6fb..0e821de87665fc2026bcdcc5fb0ca3499793b3a5 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -1391,7 +1391,7 @@ class BinaryOperation: public Expression {
       : op_(op), left_(left), right_(right), pos_(pos), is_smi_only_(false) {
     ASSERT(Token::IsBinaryOp(op));
     right_id_ = (op == Token::AND || op == Token::OR)
-        ? GetNextId()
+        ? static_cast<int>(GetNextId())
         : AstNode::kNoNumber;
   }