Add a basic custom painting facility to Sky

sky/engine/core/painting/PaintingContext.cpp

Index: sky/engine/core/painting/PaintingContext.cpp
diff --git a/sky/engine/core/painting/PaintingContext.cpp b/sky/engine/core/painting/PaintingContext.cpp
index ccd785a8bc9ed45b713bd033a6c703f5bf35e5e6..f31484580de8feef857985bf9be93099af2553f5 100644
--- a/sky/engine/core/painting/PaintingContext.cpp
+++ b/sky/engine/core/painting/PaintingContext.cpp
@@ -5,15 +5,19 @@
 #include "sky/engine/config.h"
 #include "sky/engine/core/painting/PaintingContext.h"
 
+#include "base/bind.h"
+#include "sky/engine/core/dom/Microtask.h"
 #include "sky/engine/platform/geometry/IntRect.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 
 namespace blink {
 
-PaintingContext::PaintingContext(const FloatRect& bounds)
+PaintingContext::PaintingContext(const FloatSize& size, const CommitCallback& commitCallback)
+    : m_size(size)
+    , m_commitCallback(commitCallback)
 {
-    m_displayList = adoptRef(new DisplayList(bounds));
-    m_canvas = m_displayList->beginRecording(enclosingIntRect(bounds).size());
+    m_displayList = adoptRef(new DisplayList);
+    m_canvas = m_displayList->beginRecording(expandedIntSize(size));
 }
 
 PaintingContext::~PaintingContext()
@@ -31,8 +35,11 @@ void PaintingContext::drawCircle(double x, double y, double radius, Paint* paint
 
 void PaintingContext::commit()
 {
+    if (!m_canvas)
+        return;
     m_displayList->endRecording();
     m_canvas = nullptr;
+    Microtask::enqueueMicrotask(base::Bind(m_commitCallback, this));
 }
 
 } // namespace blink