[wasm][asm.js] Make asm.js->wasm return a regular object.

src/wasm/wasm-module.cc

Index: src/wasm/wasm-module.cc
diff --git a/src/wasm/wasm-module.cc b/src/wasm/wasm-module.cc
index e4188da72a3bf1b0545c5a712c18c218ff5da8ba..0577f7e759924735c39733a9f39955cc5c0e92d4 100644
--- a/src/wasm/wasm-module.cc
+++ b/src/wasm/wasm-module.cc
@@ -1142,13 +1142,15 @@ class WasmInstanceBuilder {
  public:
   WasmInstanceBuilder(Isolate* isolate, ErrorThrower* thrower,
                       Handle<WasmModuleObject> module_object,
-                      Handle<JSReceiver> ffi, Handle<JSArrayBuffer> memory)
+                      Handle<JSReceiver> ffi, Handle<JSArrayBuffer> memory,
+                      Handle<JSObject> export_to)
       : isolate_(isolate),
         module_(module_object->compiled_module()->module()),
         thrower_(thrower),
         module_object_(module_object),
         ffi_(ffi),
-        memory_(memory) {}
+        memory_(memory),
+        export_to_(export_to) {}
 
   // Build an instance, in all of its glory.
   MaybeHandle<WasmInstanceObject> Build() {
@@ -1382,7 +1384,7 @@ class WasmInstanceBuilder {
     //--------------------------------------------------------------------------
     // Set up the exports object for the new instance.
     //--------------------------------------------------------------------------
-    ProcessExports(code_table, instance, compiled_module_);
+    ProcessExports(code_table, instance, export_to_, compiled_module_);
 
     //--------------------------------------------------------------------------
     // Add instance to Memory object
@@ -1531,6 +1533,7 @@ class WasmInstanceBuilder {
   Handle<WasmModuleObject> module_object_;
   Handle<JSReceiver> ffi_;
   Handle<JSArrayBuffer> memory_;
+  Handle<JSObject> export_to_;
   Handle<JSArrayBuffer> globals_;
   Handle<WasmCompiledModule> compiled_module_;
   std::vector<TableInstance> table_instances_;
@@ -1911,6 +1914,7 @@ class WasmInstanceBuilder {
   // and globals.
   void ProcessExports(Handle<FixedArray> code_table,
                       Handle<WasmInstanceObject> instance,
+                      Handle<JSObject> exports,
                       Handle<WasmCompiledModule> compiled_module) {
     if (NeedsWrappers()) {
       // Fill the table to cache the exported JSFunction wrappers.
@@ -1918,7 +1922,7 @@ class WasmInstanceBuilder {
                           Handle<JSFunction>::null());
     }
 
-    Handle<JSObject> exports_object = instance;
+    Handle<JSObject> exports_object = exports;
     if (module_->origin == kWasmOrigin) {
       // Create the "exports" object.
       exports_object = isolate_->factory()->NewJSObjectWithNullProto();
@@ -1928,7 +1932,7 @@ class WasmInstanceBuilder {
     }
 
     PropertyDescriptor desc;
-    desc.set_writable(false);
+    desc.set_writable(module_->origin == kAsmJsOrigin);
     desc.set_enumerable(true);
 
     // Count up export indexes.
@@ -2223,8 +2227,9 @@ class WasmInstanceBuilder {
 MaybeHandle<WasmInstanceObject> WasmModule::Instantiate(
     Isolate* isolate, ErrorThrower* thrower,
     Handle<WasmModuleObject> wasm_module, Handle<JSReceiver> ffi,
-    Handle<JSArrayBuffer> memory) {
-  WasmInstanceBuilder builder(isolate, thrower, wasm_module, ffi, memory);
+    Handle<JSArrayBuffer> memory, Handle<JSObject> export_to) {
+  WasmInstanceBuilder builder(isolate, thrower, wasm_module, ffi, memory,
+                              export_to);
   return builder.Build();
 }