Derive the SourceAlpha filter input from SourceGraphic

Source/core/svg/graphics/filters/SVGFilterBuilder.cpp

 /*
  * Copyright (C) 2009 Dirk Schulze <krit@webkit.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * 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.
  */
 
 #include "config.h"
 #include "core/svg/graphics/filters/SVGFilterBuilder.h"
 
 #include "platform/graphics/filters/SourceAlpha.h"
 #include "platform/graphics/filters/SourceGraphic.h"
 
 namespace blink {
 
-SVGFilterBuilder::SVGFilterBuilder(PassRefPtrWillBeRawPtr<FilterEffect> sourceGraphic, PassRefPtrWillBeRawPtr<FilterEffect> sourceAlpha)
+SVGFilterBuilder::SVGFilterBuilder(PassRefPtrWillBeRawPtr<FilterEffect> prpSourceGraphic)
 {
+    RefPtrWillBeRawPtr<FilterEffect> sourceGraphic = prpSourceGraphic;

[Stephen White, 2015/04/20 17:04:49]

Nit: Blink coding style prefers no abbreviations. Suggest the parameter stay
sourceGraphic, and the local become sourceGraphicRef, or something like that.

[fs, 2015/04/21 10:29:20]

Done.

     m_builtinEffects.add(SourceGraphic::effectName(), sourceGraphic);
-    m_builtinEffects.add(SourceAlpha::effectName(), sourceAlpha);
+    m_builtinEffects.add(SourceAlpha::effectName(), SourceAlpha::create(sourceGraphic.get()));
     addBuiltinEffects();
 }
 
 DEFINE_TRACE(SVGFilterBuilder)
 {
 #if ENABLE(OILPAN)
     visitor->trace(m_builtinEffects);
     visitor->trace(m_namedEffects);
     visitor->trace(m_effectRenderer);
     visitor->trace(m_effectReferences);
@@ skipping 63 matching lines @@
         return;
 
     effect->clearResult();
 
     FilterEffectSet& effectReferences = this->effectReferences(effect);
     for (FilterEffect* effectReference : effectReferences)
         clearResultsRecursive(effectReference);
 }
 
 } // namespace blink