Return Object* instead of MaybeObject* from runtime calls.

src/arguments.h

Index: src/arguments.h
diff --git a/src/arguments.h b/src/arguments.h
index b7137c3175a4f428e05748c33c7a59f4a5703feb..7e13d4b4f473dada28467677e35e0089ca1c3266 100644
--- a/src/arguments.h
+++ b/src/arguments.h
@@ -299,10 +299,10 @@ double ClobberDoubleRegisters(double x1, double x2, double x3, double x4);
 #endif
 
 
-#define DECLARE_RUNTIME_FUNCTION(Type, Name)    \
-Type Name(int args_length, Object** args_object, Isolate* isolate)
+#define DECLARE_RUNTIME_FUNCTION(Name)    \
+Object* Name(int args_length, Object** args_object, Isolate* isolate)
 
-#define RUNTIME_FUNCTION(Type, Name)                                  \
+#define RUNTIME_FUNCTION_RETURNS_TYPE(Type, Name)                     \
 static Type __RT_impl_##Name(Arguments args, Isolate* isolate);       \
 Type Name(int args_length, Object** args_object, Isolate* isolate) {  \
   CLOBBER_DOUBLE_REGISTERS();                                         \
@@ -311,6 +311,11 @@ Type Name(int args_length, Object** args_object, Isolate* isolate) {  \
 }                                                                     \
 static Type __RT_impl_##Name(Arguments args, Isolate* isolate)
 
+
+#define RUNTIME_FUNCTION(Name) RUNTIME_FUNCTION_RETURNS_TYPE(Object*, Name)
+#define RUNTIME_FUNCTION_RETURN_PAIR(Name) \
+    RUNTIME_FUNCTION_RETURNS_TYPE(ObjectPair, Name)
+
 #define RUNTIME_ARGUMENTS(isolate, args) \
   args.length(), args.arguments(), isolate