Move DragCaretController class to its own file

Source/core/paint/BlockPainter.cpp

 // 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.
 
 #include "config.h"
 #include "core/paint/BlockPainter.h"
 
+#include "core/editing/DragCaretController.h"
 #include "core/editing/FrameSelection.h"
 #include "core/frame/Settings.h"
 #include "core/layout/LayoutFlexibleBox.h"
 #include "core/layout/LayoutInline.h"
 #include "core/page/Page.h"
 #include "core/paint/BoxClipper.h"
 #include "core/paint/BoxPainter.h"
 #include "core/paint/DeprecatedPaintLayer.h"
 #include "core/paint/InlinePainter.h"
 #include "core/paint/LayoutObjectDrawingRecorder.h"
@@ skipping 328 matching lines @@
         LayoutBlock* block = flow->containingBlock();
         for ( ; block && block != &m_layoutBlock; block = block->containingBlock())
             accumulatedPaintOffset.moveBy(block->location());
         ASSERT(block);
         InlinePainter(*flow).paintOutline(info, accumulatedPaintOffset);
     }
 }
 
 
 } // namespace blink