Oilpan: fix build after r194136.

Source/bindings/core/v8/RejectedPromises.cpp

Index: Source/bindings/core/v8/RejectedPromises.cpp
diff --git a/Source/bindings/core/v8/RejectedPromises.cpp b/Source/bindings/core/v8/RejectedPromises.cpp
index 569b9457ac4a663eab1538e0b574eb2203668863..872d2b23b69fcabf5ea92f2787ef419d494536b6 100644
--- a/Source/bindings/core/v8/RejectedPromises.cpp
+++ b/Source/bindings/core/v8/RejectedPromises.cpp
@@ -64,6 +64,7 @@ DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(RejectedPromises);
 DEFINE_TRACE(RejectedPromises)
 {
     visitor->trace(m_queue);
+    visitor->trace(m_reportedAsErrors);
 }
 
 void RejectedPromises::rejectedWithNoHandler(ScriptState* scriptState, v8::PromiseRejectMessage data, const String& errorMessage, const String& resourceName, int scriptId, int lineNumber, int columnNumber, PassRefPtrWillBeRawPtr<ScriptCallStack> callStack)