Factor painting code for filters out of FilterEffectRenderer into FilterPainter.

Source/core/paint/FilterPainter.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/FilterPainter.h"
+
+#include "core/rendering/FilterEffectRenderer.h"
+#include "core/rendering/RenderLayer.h"
+#include "platform/graphics/GraphicsContext.h"
+#include "platform/graphics/filters/FilterEffect.h"
+#include "platform/graphics/filters/SkiaImageFilterBuilder.h"
+
+namespace blink {
+
+bool FilterPainter::beginFilterEffect(GraphicsContext* context, const FloatRect& filterBoxRect)
+{
+    SkiaImageFilterBuilder builder(context);
+    RefPtr<FilterEffect> lastEffect = m_renderLayer.filterRenderer()->lastEffect();
+    lastEffect->determineFilterPrimitiveSubregion(MapRectForward);
+    RefPtr<ImageFilter> imageFilter = builder.build(lastEffect.get(), ColorSpaceDeviceRGB);
+    if (!imageFilter)
+        return false;
+    context->save();
+    FloatRect boundaries = mapImageFilterRect(imageFilter.get(), filterBoxRect);
+    context->translate(filterBoxRect.x(), filterBoxRect.y());
+    boundaries.move(-filterBoxRect.x(), -filterBoxRect.y());
+    context->beginLayer(1, CompositeSourceOver, &boundaries, ColorFilterNone, imageFilter.get());
+    context->translate(-filterBoxRect.x(), -filterBoxRect.y());
+    return true;
+}
+
+void FilterPainter::endFilterEffect(GraphicsContext* context)
+{
+    context->endLayer();
+    context->restore();
+}
+
+} // namespace blink