[wasm][asm.js] Fix and enable several asm.js tests with the new parser.

test/mjsunit/wasm/asm-wasm-u32.js

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --validate-asm --allow-natives-syntax
+// Flags: --validate-asm --allow-natives-syntax --fast-validate-asm
 
 function WrapInAsmModule(func) {
   function MODULE_NAME(stdlib) {
     "use asm";
     var imul = stdlib.Math.imul;
 
     FUNC_BODY
     return {main: FUNC_NAME};
   }
 
@@ skipping 209 matching lines @@
       for (a of inputs) {
         for (b of inputs) {
           var expected = func(a, b);
           assertEquals(expected, module.main(a, b));
         }
       }
     });
   }
 
 })();