Oilpan: have WebLocalFrameImpl use SelfKeepAlive<>.

Source/web/WebLocalFrameImpl.h

 /*
  * Copyright (C) 2009 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 377 matching lines @@
 
     UserMediaClientImpl m_userMediaClientImpl;
 
     OwnPtrWillBeMember<GeolocationClientProxy> m_geolocationClientProxy;
 
     WebDevToolsFrontendImpl* m_webDevToolsFrontend;
 
     HashMap<AtomicString, OwnPtr<WebTestInterfaceFactory>> m_testInterfaces;
 
 #if ENABLE(OILPAN)
-    // Oilpan: to provide the guarantee of having the frame live until
-    // close() is called, an instance keep a self-persistent. It is
-    // cleared upon calling close(). This avoids having to assume that
-    // an embedder's WebFrame references are all discovered via thread
-    // state (stack, registers) should an Oilpan GC strike while we're
-    // in the process of detaching.
-    GC_PLUGIN_IGNORE("340522")
-    Persistent<WebLocalFrameImpl> m_selfKeepAlive;
+    // Oilpan: WebLocalFrameImpl must remain alive until close() is called.
+    // Accomplish that by keeping a self-referential Persistent<>. It is
+    // cleared upon close().
+    SelfKeepAlive<WebLocalFrameImpl> m_selfKeepAlive;
 #endif
 };
 
 DEFINE_TYPE_CASTS(WebLocalFrameImpl, WebFrame, frame, frame->isWebLocalFrame(), frame.isWebLocalFrame());
 
 } // namespace blink
 
 #endif