Oilpan: fix build after r180544.

Source/core/frame/FrameConsole.cpp

 /*
  * Copyright (C) 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 63 matching lines @@
     String messageURL;
     unsigned lineNumber = 0;
     if (consoleMessage->callStack()) {
         lineNumber = consoleMessage->callStack()->at(0).lineNumber();
         messageURL = consoleMessage->callStack()->at(0).sourceURL();
     } else {
         lineNumber = consoleMessage->lineNumber();
         messageURL = consoleMessage->url();
     }
 
-    RefPtr<ScriptCallStack> reportedCallStack;
+    RefPtrWillBeRawPtr<ScriptCallStack> reportedCallStack = nullptr;
     if (consoleMessage->source() != ConsoleAPIMessageSource) {
         if (consoleMessage->callStack() && m_frame.chromeClient().shouldReportDetailedMessageForSource(messageURL))
             reportedCallStack = consoleMessage->callStack();
     } else {
         if (!m_frame.host() || (consoleMessage->scriptArguments() && consoleMessage->scriptArguments()->argumentCount() == 0))
             return;
 
         MessageType type = consoleMessage->type();
         if (type == StartGroupMessageType || type == EndGroupMessageType || type == StartGroupCollapsedMessageType)
             return;
@@ skipping 36 matching lines @@
     ASSERT(muteCount > 0);
     muteCount--;
 }
 
 void FrameConsole::adoptWorkerConsoleMessages(WorkerGlobalScopeProxy* proxy)
 {
     InspectorInstrumentation::adoptWorkerConsoleMessages(m_frame.document(), proxy);
 }
 
 } // namespace blink