[wasm] Update WasmMemoryObject correctly when module memory is exported.

test/mjsunit/wasm/import-memory.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
 
 load("test/mjsunit/wasm/wasm-constants.js");
 load("test/mjsunit/wasm/wasm-module-builder.js");
 
 (function TestOne() {
@@ skipping 348 matching lines @@
       assertEquals(expected_pages, instances[i].exports.mem_size());
     }
   }
   var current_mem_size = 1;
   for (var i = 0; i < 10; i++) {
     function grow(pages) { return instances[i].exports.grow(pages); }
     assertEquals(current_mem_size, instances[i].exports.grow(1));
     verify_mem_size(++current_mem_size);
   }
 })();
+
+(function TestExportGrow() {
+  print("TestExportGrow");
+  let builder = new WasmModuleBuilder();
+  builder.addMemory(1, 5, true);
+  builder.exportMemoryAs("exported_mem");
+  builder.addFunction("mem_size", kSig_i_v)
+    .addBody([kExprMemorySize, kMemoryZero])
+    .exportFunc();
+  builder.addFunction("grow", kSig_i_i)
+    .addBody([kExprGetLocal, 0, kExprGrowMemory, kMemoryZero])
+    .exportFunc();
+  instance = builder.instantiate();
+  assertEquals(1, instance.exports.grow(2));
+  assertEquals(3, instance.exports.mem_size());
+  assertEquals(kPageSize, instance.exports.exported_mem.buffer.byteLength);

[gdeepti, 2016/12/04 17:48:37]

As per my understanding, this should be the correct behavior when memory is
exported as exports are returned at instantiation time. Ben, could you confirm?
Fails when guard pages are enabled, debugging bot failures. 

[titzer, 2016/12/05 09:40:54]

Yes, that's right.

[gdeepti, 2016/12/05 17:31:07]

Thanks! Bot failures fixed with latest patch. 

+})();