Change Has* and Get*Attributes to return Maybe<*>, indicating possible exceptions.

src/contexts.cc

Index: src/contexts.cc
diff --git a/src/contexts.cc b/src/contexts.cc
index cb5e852d7d669c07c8d8b950016defff1572f49c..60cf93f8d35dce48439c70b035d27cc24b2fed95 100644
--- a/src/contexts.cc
+++ b/src/contexts.cc
@@ -106,15 +106,18 @@ Handle<Object> Context::Lookup(Handle<String> name,
       // Context extension objects needs to behave as if they have no
       // prototype.  So even if we want to follow prototype chains, we need
       // to only do a local lookup for context extension objects.
+      Maybe<PropertyAttributes> maybe;
       if ((flags & FOLLOW_PROTOTYPE_CHAIN) == 0 ||
           object->IsJSContextExtensionObject()) {
-        *attributes = JSReceiver::GetOwnPropertyAttributes(object, name);
+        maybe = JSReceiver::GetOwnPropertyAttributes(object, name);
       } else {
-        *attributes = JSReceiver::GetPropertyAttributes(object, name);
+        maybe = JSReceiver::GetPropertyAttributes(object, name);
       }
-      if (isolate->has_pending_exception()) return Handle<Object>();
+      if (!maybe.has_value) return Handle<Object>();
+      ASSERT(!isolate->has_pending_exception());
+      *attributes = maybe.value;
 
-      if (*attributes != ABSENT) {
+      if (maybe.value != ABSENT) {
         if (FLAG_trace_contexts) {
           PrintF("=> found property in context object %p\n",
                  reinterpret_cast<void*>(*object));