Don't include LayoutObject-derived headers where not needed.

third_party/WebKit/Source/core/layout/FragmentainerIterator.h

 // Copyright 2016 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 FragmentainerIterator_h
 #define FragmentainerIterator_h
 
-#include "core/layout/LayoutFlowThread.h"
+#include "platform/geometry/LayoutRect.h"
 
 namespace blink {
 
+class LayoutFlowThread;
+class LayoutMultiColumnSet;
 class MultiColumnFragmentainerGroup;
 
 // Used to find the fragmentainers that intersect with a given portion of the
 // flow thread. The portion typically corresponds to the bounds of some
 // descendant layout object. The iterator walks in block direction order.
 class FragmentainerIterator {
  public:
   // Initialize the iterator, and move to the first fragmentainer of interest.
   // The clip rectangle is optional. If it's empty, it means that no clipping
   // will be performed, and that the only thing that can limit the set of
@@ skipping 37 matching lines @@
   const MultiColumnFragmentainerGroup& currentGroup() const;
   void moveToNextFragmentainerGroup();
   bool setFragmentainersOfInterest();
   void setAtEnd() { m_currentColumnSet = nullptr; }
   bool hasClipRect() const { return !m_clipRectInMulticolContainer.isEmpty(); }
 };
 
 }  // namespace blink
 
 #endif  // FragmentainerIterator_h