Derive the SourceAlpha filter input from SourceGraphic

Source/core/paint/SVGFilterPainter.cpp

 // Copyright 2015 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/SVGFilterPainter.h"
 
 #include "core/layout/PaintInfo.h"
 #include "core/layout/svg/LayoutSVGResourceFilter.h"
 #include "core/paint/CompositingRecorder.h"
 #include "core/paint/LayoutObjectDrawingRecorder.h"
 #include "core/paint/TransformRecorder.h"
 #include "platform/graphics/filters/SkiaImageFilterBuilder.h"
-#include "platform/graphics/filters/SourceAlpha.h"
 #include "platform/graphics/filters/SourceGraphic.h"
 #include "platform/graphics/paint/CompositingDisplayItem.h"
 #include "platform/graphics/paint/DisplayItemList.h"
 #include "platform/graphics/paint/DrawingDisplayItem.h"
 
 namespace blink {
 
 static GraphicsContext* beginRecordingContent(GraphicsContext* context, FilterData* filterData)
 {
     ASSERT(filterData->m_state == FilterData::Initial);
@@ skipping 166 matching lines @@
 
     LayoutObjectDrawingRecorder recorder(*context, object, DisplayItem::SVGFilter, LayoutRect::infiniteIntRect());
     if (recorder.canUseCachedDrawing())
         return;
 
     if (filterData && filterData->m_state == FilterData::ReadyToPaint)
         paintFilteredContent(context, filterData, toSVGFilterElement(m_filter.element()));
 }
 
 }