[Isolates] Merge (7083,7111] from bleeding_edge.

src/handles.h

Index: src/handles.h
diff --git a/src/handles.h b/src/handles.h
index 632272e0e76e6a0e4194de81775d97680a63355d..1ad0ee9a65be14275c00b793a986b2cceb61ed64 100644
--- a/src/handles.h
+++ b/src/handles.h
@@ -226,10 +226,10 @@ Handle<Object> SetPropertyWithInterceptor(Handle<JSObject> object,
                                           PropertyAttributes attributes,
                                           StrictModeFlag strict_mode);
 
-Handle<Object> SetElement(Handle<JSObject> object,
-                          uint32_t index,
-                          Handle<Object> value,
-                          StrictModeFlag strict_mode);
+MUST_USE_RESULT Handle<Object> SetElement(Handle<JSObject> object,
+                                          uint32_t index,
+                                          Handle<Object> value,
+                                          StrictModeFlag strict_mode);
 
 Handle<Object> SetOwnElement(Handle<JSObject> object,
                              uint32_t index,