Oilpan: have WebRemoteFrameImpl use SelfKeepAlive<>.

Source/web/WebRemoteFrameImpl.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef WebRemoteFrameImpl_h
 #define WebRemoteFrameImpl_h
 
 #include "core/frame/FrameOwner.h"
 #include "platform/heap/Handle.h"
 #include "public/web/WebRemoteFrame.h"
@@ skipping 184 matching lines @@
 private:
     WebRemoteFrameImpl(WebTreeScopeType, WebRemoteFrameClient*);
 
     RemoteFrameClientImpl m_frameClient;
     RefPtrWillBeMember<RemoteFrame> m_frame;
     WebRemoteFrameClient* m_client;
 
     WillBeHeapHashMap<WebFrame*, OwnPtrWillBeMember<FrameOwner>> m_ownersForChildren;
 
 #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<WebRemoteFrameImpl> m_selfKeepAlive;
+    // Oilpan: WebRemoteFrameImpl must remain alive until close() is called.
+    // Accomplish that by keeping a self-referential Persistent<>. It is
+    // cleared upon close().
+    SelfKeepAlive<WebRemoteFrameImpl> m_selfKeepAlive;
 #endif
 };
 
 DEFINE_TYPE_CASTS(WebRemoteFrameImpl, WebFrame, frame, frame->isWebRemoteFrame(), frame.isWebRemoteFrame());
 
 } // namespace blink
 
 #endif // WebRemoteFrameImpl_h