[promises] port NewPromiseCapability to TF

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 951199d8166568caac66afe426a4299c92e3d172..53d9569634ac6d09ebad96112f915d4003377482 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -2267,6 +2267,9 @@ bool Heap::CreateInitialMaps() {
     ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, optimized_out);
     ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, stale_register);
 
+    ALLOCATE_MAP(JS_PROMISE_CAPABILITY_TYPE, JSPromiseCapability::kSize,
+                 js_promise_capability);
+
     for (unsigned i = 0; i < arraysize(string_type_table); i++) {
       const StringTypeTable& entry = string_type_table[i];
       {
@@ -2873,6 +2876,42 @@ void Heap::CreateInitialObjects() {
 
   // Initialize compilation cache.
   isolate_->compilation_cache()->Clear();
+
+  // Finish creating JSPromiseCapabilityMap
+  {
+    // TODO(caitp): This initialization can be removed once PromiseCapability
+    // object is no longer used by builtins implemented in javascript.
+    Handle<Map> map = factory->js_promise_capability_map();
+    map->set_inobject_properties_or_constructor_function_index(3);
+
+    Map::EnsureDescriptorSlack(map, 3);
+
+    PropertyAttributes attrs =
+        static_cast<PropertyAttributes>(READ_ONLY | DONT_DELETE);
+    {  // promise
+      DataDescriptor d(factory->promise_string(),
+                       JSPromiseCapability::kPromiseIndex, attrs,
+                       Representation::Tagged());
+      map->AppendDescriptor(&d);
+    }
+
+    {  // resolve
+      DataDescriptor d(factory->resolve_string(),
+                       JSPromiseCapability::kResolveIndex, attrs,
+                       Representation::Tagged());
+      map->AppendDescriptor(&d);
+    }
+
+    {  // reject
+      DataDescriptor d(factory->reject_string(),
+                       JSPromiseCapability::kRejectIndex, attrs,
+                       Representation::Tagged());
+      map->AppendDescriptor(&d);
+    }

[gsathya, 2016/12/21 01:02:33]

Honestly I feel like we could just use runtime calls for now

[caitp, 2016/12/21 21:01:13]

To me, it seemed simpler to let it use in-object stuff. Once there's no JS code
that needs to look at these objects, it will be safe to get rid of this gunk and
make the PromiseCapability a Struct with a dead simple Map, and slightly smaller
size on the heap.

+
+    map->set_is_extensible(false);
+    set_js_promise_capability_map(*map);
+  }
 }
 
 bool Heap::RootCanBeWrittenAfterInitialization(Heap::RootListIndex root_index) {