Reland^2 "Don't compile functions in a context the caller doesn't have access to"

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index e20cd1a6ef4169598d8f47a4b93097c8d15d4eb9..ddd90b5a275077e8f5571168987656eac144dfbb 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -2887,10 +2887,13 @@ void Isolate::RunMicrotasksInternal() {
             Handle<JSFunction>::cast(microtask);
         SaveContext save(this);
         set_context(microtask_function->context()->native_context());
+        handle_scope_implementer_->EnterMicrotaskContext(
+            handle(microtask_function->context(), this));
         MaybeHandle<Object> maybe_exception;
         MaybeHandle<Object> result = Execution::TryCall(
             this, microtask_function, factory()->undefined_value(), 0, NULL,
             &maybe_exception);
+        handle_scope_implementer_->LeaveMicrotaskContext();
         // If execution is terminating, just bail out.
         Handle<Object> exception;
         if (result.is_null() && maybe_exception.is_null()) {