Use the stateless GC::fillRect variant when possible.

Source/core/paint/LayerPainter.cpp

Index: Source/core/paint/LayerPainter.cpp
diff --git a/Source/core/paint/LayerPainter.cpp b/Source/core/paint/LayerPainter.cpp
index 7e5e198553306c4640200749e3eaa5f13216dbfa..65db44e59990aca1aeb75a83d5a2dbc30306aea4 100644
--- a/Source/core/paint/LayerPainter.cpp
+++ b/Source/core/paint/LayerPainter.cpp
@@ -138,8 +138,7 @@ void LayerPainter::beginTransparencyLayers(GraphicsContext* context, const Rende
         if (m_renderLayer.paintsWithBlendMode())
             context->setCompositeOperation(context->compositeOperation(), WebBlendModeNormal);
 #ifdef REVEAL_TRANSPARENCY_LAYERS
-        context->setFillColor(Color(0.0f, 0.0f, 0.5f, 0.2f));
-        context->fillRect(clipRect);
+        context->fillRect(clipRect, Color(0.0f, 0.0f, 0.5f, 0.2f));
 #endif
     }
 }