[wasm] Memory buffer should be detached after Memory.Grow

test/mjsunit/wasm/js-api.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: --expose-wasm --allow-natives-syntax
 
 if ((typeof drainJobQueue) != "function") {
   drainJobQueue = () => { %RunMicrotasks() };
 }
 
@@ skipping 451 matching lines @@
 var mem = new Memory({initial:1, maximum:2});
 var buf = mem.buffer;
 assertEq(buf.byteLength, kPageSize);
 assertEq(mem.grow(0), 1);
 // TODO(gdeepti): Pending spec clarification
 // assertTrue(buf !== mem.buffer);
 // assertEq(buf.byteLength, 0);
 buf = mem.buffer;
 assertEq(buf.byteLength, kPageSize);
 assertEq(mem.grow(1), 1);
-// TODO(gdeepti): assertTrue(buf !== mem.buffer);
-// TODO(gdeepti): assertEq(buf.byteLength, 0);
+assertTrue(buf !== mem.buffer);
+assertEq(buf.byteLength, 0);
 buf = mem.buffer;
 assertEq(buf.byteLength, 2 * kPageSize);
 assertErrorMessage(() => mem.grow(1), Error, /failed to grow memory/);
 assertEq(buf, mem.buffer);
 
 // 'WebAssembly.Table' data property
 let tableDesc = Object.getOwnPropertyDescriptor(WebAssembly, 'Table');
 assertEq(typeof tableDesc.value, "function");
 assertTrue(tableDesc.writable);
 assertFalse(tableDesc.enumerable);
@@ skipping 222 matching lines @@
     assertTrue(result.instance instanceof Instance);
   }
 }
 assertInstantiateSuccess(emptyModule);
 assertInstantiateSuccess(emptyModuleBinary);
 assertInstantiateSuccess(emptyModuleBinary.buffer);
 assertInstantiateSuccess(importingModule, {'': {f: () => {}}});
 assertInstantiateSuccess(importingModuleBinary, {"":{f:()=>{}}});
 assertInstantiateSuccess(importingModuleBinary.buffer, {"":{f:()=>{}}});
 assertInstantiateSuccess(memoryImportingModuleBinary, {"": {"my_memory": scratch_memory}});