[wasm][asm.js] Require exported asm.js functions have be names.

test/mjsunit/wasm/asm-wasm.js

 // Copyright 2015 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
 
 var stdlib = this;
 
 function assertValidAsm(func) {
   assertTrue(%IsAsmWasmCode(func));
@@ skipping 1466 matching lines @@
       return (x & y) | 0;
     }
     return {func: func};
   }
 
   Module(stdlib);
   assertTrue(%IsNotAsmWasmCode(Module));
 })();
 
 
+(function TestBadExportKey() {
+  function Module() {
+    "use asm";
+    function func() {
+    }
+    return {123: func};
+  }
+
+  Module(stdlib);
+  assertTrue(%IsNotAsmWasmCode(Module));
+})();
+
+
 function TestAndIntAndHeapValue(stdlib, foreign, buffer) {
   "use asm";
   var HEAP32 = new stdlib.Int32Array(buffer);
   function func() {
     var x = 0;
     x = HEAP32[0] & -1;
     return x | 0;
   }
   return {caller: func};
 }
@@ skipping 211 matching lines @@
     "use asm";
     function foo() {
       return 42;
     }
     return {bar: foo, baz: foo};
   }
   var m = asmModule();
   assertEquals(42, m.bar());
   assertEquals(42, m.baz());
 })();