Don't include headers from the layout API from other headers needlessly.

third_party/WebKit/Source/core/frame/Frame.h

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999-2001 Lars Knoll <knoll@kde.org>
  *                     1999-2001 Antti Koivisto <koivisto@kde.org>
  *                     2000-2001 Simon Hausmann <hausmann@kde.org>
  *                     2000-2001 Dirk Mueller <mueller@kde.org>
  *                     2000 Stefan Schimanski <1Stein@gmx.de>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
@@ skipping 12 matching lines @@
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 #ifndef Frame_h
 #define Frame_h
 
 #include "core/CoreExport.h"
 #include "core/frame/FrameTypes.h"
-#include "core/layout/api/LayoutPartItem.h"
 #include "core/loader/FrameLoaderTypes.h"
 #include "core/page/FrameTree.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Forward.h"
 
 namespace blink {
 
 class ChromeClient;
 class DOMWindow;
 class DOMWrapperWorld;
 class Document;
 class FrameClient;
 class FrameHost;
 class FrameOwner;
 class HTMLFrameOwnerElement;
 class LayoutPart;
+class LayoutPartItem;
 class KURL;
 class Page;
 class SecurityContext;
 class Settings;
 class WindowProxy;
 class WindowProxyManager;
 struct FrameLoadRequest;
 
 enum class FrameDetachType { Remove, Swap };
 
@@ skipping 53 matching lines @@
     // Returns true if the frame is ready to receive the next commit, or false
     // otherwise.
     virtual bool prepareForCommit() = 0;
 
     bool canNavigate(const Frame&);
     virtual void printNavigationErrorMessage(const Frame&, const char* reason) = 0;
 
     // TODO(pilgrim) replace all instances of ownerLayoutObject() with ownerLayoutItem()
     // https://crbug.com/499321
     LayoutPart* ownerLayoutObject() const; // LayoutObject for the element that contains this frame.
-    LayoutPartItem ownerLayoutItem() const
-    {
-        return LayoutPartItem(this->ownerLayoutObject());
-    }
+    LayoutPartItem ownerLayoutItem() const;
 
     Settings* settings() const; // can be null
 
     // isLoading() is true when the embedder should think a load is in progress.
     // In the case of LocalFrames, it means that the frame has sent a didStartLoading()
     // callback, but not the matching didStopLoading(). Inside blink, you probably
     // want Document::loadEventFinished() instead.
     void setIsLoading(bool isLoading) { m_isLoading = isLoading; }
     bool isLoading() const { return m_isLoading; }
 
@@ skipping 30 matching lines @@
 {
     return m_treeNode;
 }
 
 // Allow equality comparisons of Frames by reference or pointer, interchangeably.
 DEFINE_COMPARISON_OPERATORS_WITH_REFERENCES(Frame)
 
 } // namespace blink
 
 #endif // Frame_h