Implement Instance instances correctly; fix a few error cases

test/mjsunit/wasm/module-memory.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: --expose-wasm --expose-gc --stress-compaction
 
 load("test/mjsunit/wasm/wasm-constants.js");
 load("test/mjsunit/wasm/wasm-module-builder.js");
 
 var kMemSize = 65536;
@@ skipping 18 matching lines @@
       /*    */ kExprGetLocal, 0,           // --
       /*    */ kExprI32Const, 4,           // --
       /*    */ kExprI32Sub,                // --
       /*    */ kExprSetLocal, 0,           // --
       /*    */ kExprBr, 1,                 // --
       /*    */ kExprEnd,                   // --
       /*  */ kExprEnd,                     // --
       /**/ kExprI32Const, 0                // --
     ])
     .exportFunc();
-  var module = builder.instantiate(null, memory);
+  var module = builder.instantiate(undefined, memory);
   assertTrue(module.exports.memory instanceof WebAssembly.Memory);
   if (memory != null) assertEquals(memory.buffer, module.exports.memory.buffer);
   return module;
 }
 
 function testPokeMemory() {
   print("testPokeMemory");
-  var module = genModule(null);
+  var module = genModule(undefined);
   var buffer = module.exports.memory.buffer;
   var main = module.exports.main;
   assertEquals(kMemSize, buffer.byteLength);
 
   var array = new Int8Array(buffer);
   assertEquals(kMemSize, array.length);
 
   for (var i = 0; i < kMemSize; i++) {
     assertEquals(0, array[i]);
   }
@@ skipping 10 matching lines @@
   }
 }
 
 testPokeMemory();
 
 function genAndGetMain(buffer) {
   return genModule(buffer).exports.main;  // to prevent intermediates living
 }
 
 function testSurvivalAcrossGc() {
-  var checker = genAndGetMain(null);
+  var checker = genAndGetMain(undefined);
   for (var i = 0; i < 3; i++) {
     print("gc run ", i);
     assertEquals(0, checker(kMemSize - 4));
     gc();
   }
 }
 
 testSurvivalAcrossGc();
 testSurvivalAcrossGc();
 testSurvivalAcrossGc();
@@ skipping 71 matching lines @@
   }
 
 
   for (offset = 65534; offset < 66536; offset++) {
     assertTraps(kTrapMemOutOfBounds, read);
     assertTraps(kTrapMemOutOfBounds, write);
   }
 }
 
 testOOBThrows();