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

test/mjsunit/wasm/import-memory.js

Index: test/mjsunit/wasm/import-memory.js
diff --git a/test/mjsunit/wasm/import-memory.js b/test/mjsunit/wasm/import-memory.js
index 3b70332f97bc5eb95d2dbd81135df3a89204d0c2..2b6c7567089062e3172e512109d8caea53cf8776 100644
--- a/test/mjsunit/wasm/import-memory.js
+++ b/test/mjsunit/wasm/import-memory.js
@@ -366,3 +366,20 @@ load("test/mjsunit/wasm/wasm-module-builder.js");
     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. 

+})();