Remove unused includes from core/html .cpp files

Source/core/html/shadow/SliderThumbElement.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 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.
@@ skipping 15 matching lines @@
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 
 #include "config.h"
 #include "core/html/shadow/SliderThumbElement.h"
 
-#include "CSSValueKeywords.h"
 #include "core/dom/Event.h"
 #include "core/dom/MouseEvent.h"
-#include "core/dom/shadow/ElementShadow.h"
 #include "core/dom/shadow/ShadowRoot.h"
 #include "core/html/HTMLInputElement.h"
 #include "core/html/StepRange.h"
 #include "core/html/parser/HTMLParserIdioms.h"
 #include "core/page/EventHandler.h"
 #include "core/page/Frame.h"
 #include "core/rendering/RenderFlexibleBox.h"
 #include "core/rendering/RenderSlider.h"
 #include "core/rendering/RenderTheme.h"
 #include <wtf/MathExtras.h>
@@ skipping 422 matching lines @@
     case MediaVolumeSliderThumbPart:
     case MediaFullScreenVolumeSliderPart:
     case MediaFullScreenVolumeSliderThumbPart:
         return mediaSliderContainer;
     default:
         return sliderContainer;
     }
 }
 
 }