[wasm] Do a proper HasProperty() check in the memory and table setup.

test/mjsunit/wasm/memory.js

Index: test/mjsunit/wasm/memory.js
diff --git a/test/mjsunit/wasm/memory.js b/test/mjsunit/wasm/memory.js
index a90d44c41ad8607c166d853ea69be316f7e7f8b4..b6f2ce3c605aee9224a593b8ac5937f80af076a3 100644
--- a/test/mjsunit/wasm/memory.js
+++ b/test/mjsunit/wasm/memory.js
@@ -42,6 +42,15 @@ var outOfUint32RangeValue = 1e12;
   assertTrue(memory instanceof WebAssembly.Memory);
 })();
 
+(function TestInitialIsUndefined() {

[Franzi, 2016/09/23 17:23:28]

I think this test passes without your change as well. Can we add a test for
{maximum: undefined} which should now behave like {maximum: 0} and not anymore
like {}? 

And, just to be safe, we could add one, where initial and maximum are not an own
property but on the prototype.

If you want to go all out, write a test for an accessor. This way we know if we
call HasProperty() according to the spec. Something like this:

var a = true;
var desc = {};
Object.defineProperty(desc, 'maximum', {get: function() {
  if (a) {a = false; return 32766;}
  else {return -1;} // change the return value on the second call so it throws
}}); 
let memory = new WebAssembly.Memory(desc);

[ahaas, 2016/09/26 09:19:12]

Done, and I also added many more tests.

+  // New memory with initial = undefined, which means initial = 0.
+  let memory = new WebAssembly.Memory({initial: undefined});
+  assertSame(WebAssembly.Memory.prototype, memory.__proto__);
+  assertSame(WebAssembly.Memory, memory.constructor);
+  assertTrue(memory instanceof Object);
+  assertTrue(memory instanceof WebAssembly.Memory);
+})();
+
 (function TestBuffer() {
   let memory = new WebAssembly.Memory({initial: 1});
   assertTrue(memory.buffer instanceof Object);