Adds filter support for offscreen canvas

third_party/WebKit/Source/core/paint/FilterEffectBuilder.cpp

 /*
  * Copyright (C) 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2013 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 102 matching lines @@
   matrix.uncheckedAppend(clampTo<float>(0.534 - 0.534 * oneMinusAmount));
   matrix.uncheckedAppend(clampTo<float>(0.131 + 0.869 * oneMinusAmount));
   endMatrixRow(matrix);
 
   lastMatrixRow(matrix);
   return matrix;
 }
 
 }  // namespace
 
+FilterEffectBuilder::FilterEffectBuilder(const FloatRect& zoomedReferenceBox,
+                                         float zoom,
+                                         const SkPaint* fillPaint,
+                                         const SkPaint* strokePaint) {
+  FilterEffectBuilder(nullptr, zoomedReferenceBox, zoom, fillPaint,
+                      strokePaint);
+}
+
 FilterEffectBuilder::FilterEffectBuilder(Node* target,
                                          const FloatRect& zoomedReferenceBox,
                                          float zoom,
                                          const SkPaint* fillPaint,
                                          const SkPaint* strokePaint)
     : m_targetContext(target),
       m_referenceBox(zoomedReferenceBox),
       m_zoom(zoom),
       m_fillPaint(fillPaint),
       m_strokePaint(strokePaint) {
@@ skipping 297 matching lines @@
       Filter::create(m_referenceBox, filterRegion, m_zoom, unitScaling);
   if (!previousEffect)
     previousEffect = result->getSourceGraphic();
   SVGFilterBuilder builder(previousEffect, nodeMap, m_fillPaint, m_strokePaint);
   builder.buildGraph(result, filterElement, m_referenceBox);
   result->setLastEffect(builder.lastEffect());
   return result;
 }
 
 }  // namespace blink