Refactor shadow rendering logic.

Source/core/platform/graphics/DrawLooper.h

Index: Source/core/platform/graphics/DrawLooper.h
diff --git a/Source/core/css/resolver/TransformBuilder.h b/Source/core/platform/graphics/DrawLooper.h
similarity index 56%
copy from Source/core/css/resolver/TransformBuilder.h
copy to Source/core/platform/graphics/DrawLooper.h
index 8807205dac541fa3339f15c2e4bba92f22763d44..6bfdfc4ffe74c526e19b12298461bd0647e711b0 100644
--- a/Source/core/css/resolver/TransformBuilder.h
+++ b/Source/core/platform/graphics/DrawLooper.h
@@ -28,26 +28,53 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef TransformBuilder_h
-#define TransformBuilder_h
+#ifndef DrawLooper_h
+#define DrawLooper_h
 
-#include "core/platform/graphics/transforms/TransformOperations.h"
+#include "third_party/skia/include/core/SkDrawLooper.h"
+
+// SkPaint and SkPoint are needed before SkLayerDrawLooper.h; they should be #included there.
+// Can be removed once https://codereview.chromium.org/14607015/ is submitted.
+#include "third_party/skia/include/core/SkPaint.h"
+#include "third_party/skia/include/core/SkPoint.h"
+
+#include "third_party/skia/include/core/SkRefCnt.h"
+#include "third_party/skia/include/effects/SkLayerDrawLooper.h"
 #include "wtf/Noncopyable.h"
 
 namespace WebCore {
 
-class RenderStyle;
-class CSSValue;
+class Color;
+class FloatSize;
+
+class DrawLooper {
+    // Implementing the copy constructor properly would require writing code to
+    // copy the underlying SkDrawLooper.
+    WTF_MAKE_NONCOPYABLE(DrawLooper);
 
-class TransformBuilder {
-    WTF_MAKE_NONCOPYABLE(TransformBuilder); WTF_MAKE_FAST_ALLOCATED;
 public:
-    TransformBuilder();
-    ~TransformBuilder();
+    enum ShadowTransformMode {
+        ShadowRespectsTransforms,
+        ShadowIgnoresTransforms
+    };
+    enum ShadowAlphaMode {
+        ShadowRespectsAlpha,
+        ShadowIgnoresAlpha
+    };
+
+    DrawLooper();
+    ~DrawLooper() { }
+    SkLayerDrawLooper* skDrawLooper() { return m_skDrawLooper.get(); }
+
+    void addUnmodifiedContent();
+    void addShadow(const FloatSize& offset, float blur, const Color&,
+        ShadowTransformMode = ShadowRespectsTransforms,
+        ShadowAlphaMode = ShadowRespectsAlpha);
 
-    static bool createTransformOperations(CSSValue* inValue, RenderStyle* inStyle, RenderStyle* rootStyle, TransformOperations& outOperations);
+private:
+    SkAutoTUnref<SkLayerDrawLooper> m_skDrawLooper;
 };
 
 } // namespace WebCore
 
-#endif // TransformBuilder_h
+#endif // DrawLooper_h