Sky: Add a DrawLooper interface to the painting API to be used for shadows.

sky/engine/core/painting/LayerDrawLooperBuilder.cpp

Index: sky/engine/core/painting/LayerDrawLooperBuilder.cpp
diff --git a/sky/engine/core/painting/LayerDrawLooperBuilder.cpp b/sky/engine/core/painting/LayerDrawLooperBuilder.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..13072f77979104a4eeb87a3fed41145e53da8804
--- /dev/null
+++ b/sky/engine/core/painting/LayerDrawLooperBuilder.cpp
@@ -0,0 +1,45 @@
+// 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 "sky/engine/config.h"
+#include "sky/engine/core/painting/LayerDrawLooperBuilder.h"
+
+#include "sky/engine/core/painting/DrawLooper.h"
+#include "sky/engine/core/painting/DrawLooperAddLayerCallback.h"
+#include "sky/engine/core/painting/DrawLooperLayerInfo.h"
+#include "sky/engine/core/painting/Paint.h"
+#include "third_party/skia/include/core/SkColorFilter.h"
+
+namespace blink {
+
+LayerDrawLooperBuilder::LayerDrawLooperBuilder() {
+}
+
+LayerDrawLooperBuilder::~LayerDrawLooperBuilder() {
+}
+
+PassRefPtr<DrawLooper> LayerDrawLooperBuilder::build() {
+  return DrawLooper::create(adoptRef(draw_looper_builder_.detachLooper()));
+}
+
+void LayerDrawLooperBuilder::addLayerOnTop(
+    DrawLooperLayerInfo* layer_info,
+    PassOwnPtr<DrawLooperAddLayerCallback> callback) {
+  SkPaint* sk_paint =
+      draw_looper_builder_.addLayerOnTop(layer_info->layer_info());
+  RefPtr<Paint> paint = Paint::create();
+
+  paint->setPaint(*sk_paint);
+  callback->handleEvent(paint.get());
+  *sk_paint = paint->paint();
+
+  // TODO(mpcomplete): Remove this when we add color filter support to Paint's
+  // API.
+  SkColor skColor = sk_paint->getColor();
+  RefPtr<SkColorFilter> cf = adoptRef(
+      SkColorFilter::CreateModeFilter(skColor, SkXfermode::kSrcIn_Mode));
+  sk_paint->setColorFilter(cf.get());
+}
+
+} // namespace blink