Desugar async/await to create the resulting Promise upfront

src/accessors.cc

Index: src/accessors.cc
diff --git a/src/accessors.cc b/src/accessors.cc
index da44151b3edbdd6d4b517e14936aacc83bd0b6fc..8d7fac5d3cd279a9f87bada7e33a6a520851ee1d 100644
--- a/src/accessors.cc
+++ b/src/accessors.cc
@@ -737,7 +737,12 @@ void Accessors::FunctionLengthGetter(
   Handle<JSFunction> function =
       Handle<JSFunction>::cast(Utils::OpenHandle(*info.Holder()));
   Handle<Object> result;
-  if (!JSFunction::GetLength(isolate, function).ToHandle(&result)) {
+  // This may invoke the compiler, so check for stack overflow like other
+  // compiler entrypoints, and return 0 on failure (as on an exception).
+  StackLimitCheck check(isolate);
+  if (check.JsHasOverflowed(1 * KB)) {
+    result = handle(Smi::FromInt(0), isolate);

[caitp, 2016/08/12 01:57:10]

thinking about this, we only want to return 0 if compiling is actually needed,
right? Are we not able to move this to JSFunction::GetLength()?

[Dan Ehrenberg, 2016/08/12 02:20:47]

I backed out this change in the most recent version. Now, it'll throw an
exception and go down the exception path because of the stack overflow from
within fullcodegen.

+  } else if (!JSFunction::GetLength(isolate, function).ToHandle(&result)) {
     result = handle(Smi::FromInt(0), isolate);
     isolate->OptionalRescheduleException(false);
   }