Reduce boilerplace for common pattern to return MaybeHandle.

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index 40f0c0ea5c93e3ae13bacfa9b832273c0e1d0133..57c17fe5832d5812b48dd127e9ac1444e88b9dbc 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -124,6 +124,16 @@ typedef ZoneList<Handle<Object> > ZoneObjectList;
 #define RETURN_EXCEPTION_IF_SCHEDULED_EXCEPTION(isolate, T) \
   RETURN_VALUE_IF_SCHEDULED_EXCEPTION(isolate, MaybeHandle<T>())
 
+#define RETURN_RESULT_OR_FAILURE(isolate, call)   \
+  do {                                            \
+    Handle<Object> __result__;                    \
+    if (!(call).ToHandle(&__result__)) {          \
+      DCHECK((isolate)->has_pending_exception()); \
+      return isolate->heap()->exception();        \

[Jakob Kummerow, 2016/05/24 09:16:21]

It seems inconsistent that the DCHECK line puts parentheses around (isolate) but
this line doesn't. If we want to be robust against funky expressions being used
as inputs we should be so everywhere.

[Yang, 2016/05/24 11:07:21]

you are right. We actually have this problem below as well. Will fix.

+    }                                             \
+    return *__result__;                           \
+  } while (false)
+
 #define ASSIGN_RETURN_ON_EXCEPTION_VALUE(isolate, dst, call, value)  \
   do {                                                               \
     if (!(call).ToHandle(&dst)) {                                    \