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

sky/engine/core/painting/DrawLooperLayerInfo.idl

+// 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.
+
+[
+  Constructor(),
+] interface DrawLooperLayerInfo {
+  // Bits specifies which aspects of the layer's paint should replace the
+  // corresponding aspects on the draw's paint.
+  // ENTIRE_PAINT_BITS means use the layer's paint completely.
+  // 0 means ignore the layer's paint... except for colorMode, which is
+  // always applied.
+  // TODO(mpcomplete): maybe these should each be functions (e.g. useStyle()).
+  // TODO(mpcomplete): the IDL compiler doesn't use these for anything?
+  const unsigned long STYLE_BIT        = 0x1;
+  const unsigned long TEXT_SKEWX_BIT   = 0x2;
+  const unsigned long PATH_EFFECT_BIT  = 0x4;
+  const unsigned long MASK_FILTER_BIT  = 0x8;
+  const unsigned long SHADER_BIT       = 0x10;
+  const unsigned long COLOR_FILTER_BIT = 0x20;
+  const unsigned long XFERMODE_BIT     = 0x40;
+  const unsigned long ENTIRE_PAINT_BITS = -1;
+
+  void setPaintBits(unsigned long bits);
+  // TODO(mpcomplete): use SkXfermode::Mode.
+  void setColorMode(unsigned long mode);
+  // TODO(mpcomplete): use Point.
+  void setOffset(float x, float y);
+  void setPostTranslate(boolean postTranslate);
+};