Sky: Add a CustomDart attribute to the IDL compiler, and use that with Canvas

sky/engine/core/painting/Canvas.cpp

 // 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/PictureRecorder.h"
 
 #include "sky/engine/core/dom/Document.h"
 #include "sky/engine/core/dom/Element.h"
 #include "sky/engine/core/painting/PaintingTasks.h"
@@ skipping 102 matching lines @@
 
 void Canvas::drawPicture(Picture* picture)
 {
     if (!m_canvas)
         return;
     ASSERT(picture);
     ASSERT(m_displayList->isRecording());
     m_canvas->drawPicture(picture->displayList()->picture());
 }
 
-void Canvas::drawPaint(Paint* paint)
+void Canvas::drawPaint(const Paint* paint)
 {
     if (!m_canvas)
         return;
     ASSERT(paint);
     ASSERT(m_displayList->isRecording());
     m_canvas->drawPaint(paint->paint());
 }
 
 void Canvas::drawRect(const Vector<float>& rect, const Paint* paint)
 {
     if (!m_canvas)
         return;
     ASSERT(paint);
     ASSERT(m_displayList->isRecording());
     m_canvas->drawRect(toSkRect(rect), paint->paint());
 }
 
 void Canvas::drawOval(const Vector<float>& rect, const Paint* paint)
 {
     if (!m_canvas)
         return;
     ASSERT(paint);
     ASSERT(m_displayList->isRecording());
     m_canvas->drawOval(toSkRect(rect), paint->paint());
 }
 
-void Canvas::drawCircle(float x, float y, float radius, Paint* paint)
+void Canvas::drawCircle(float x, float y, float radius, const Paint* paint)
 {
     if (!m_canvas)
         return;
     ASSERT(paint);
     ASSERT(m_displayList->isRecording());
     m_canvas->drawCircle(x, y, radius, paint->paint());
 }
 
 PassRefPtr<DisplayList> Canvas::finishRecording()
 {
     if (!isRecording())
         return nullptr;
     m_canvas = nullptr;
     m_displayList->endRecording();
     return m_displayList.release();
 }
 
 } // namespace blink