[wasm] Cleanup %IsAsmWasmCode testing predicate.

test/mjsunit/asm/asm-validation.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
 
+// Note that this test file contains tests that explicitly check modules are
+// valid asm.js and then break them with invalid instantiation arguments. If
+// this script is run more than once (e.g. --stress-opt) then modules remain
+// broken in the second run and assertions would fail. We prevent re-runs.
+// Flags: --nostress-opt
+
 function assertValidAsm(func) {
   assertTrue(%IsAsmWasmCode(func));
 }
 
 (function TestConst() {
   function Module(s) {
     "use asm";
     var fround = s.Math.fround;
     // Global constants. These are treated just like numeric literals.
     const fConst = fround(-3.0);
@@ skipping 305 matching lines @@
           return 43;
       }
       return 0;
     }
     return { foo: foo };
   }
   var m = Module();
   assertTrue(%IsNotAsmWasmCode(Module));
   assertEquals(43, m.foo(3));
 })();