GraphicsContext culling support.

Source/platform/graphics/GraphicsContextCullSaver.h

+#ifndef GraphicsContextCullSaver_h
+#define GraphicsContextCullSaver_h
+
+#include "platform/graphics/GraphicsContext.h"
+
+namespace WebCore {
+
+class FloatRect;
+
+class GraphicsContextCullSaver {
+    WTF_MAKE_FAST_ALLOCATED;
+public:
+    GraphicsContextCullSaver(GraphicsContext& context)
+        : m_context(context)
+        , m_cullApplied(false)
+    {
+    }
+
+    GraphicsContextCullSaver(GraphicsContext& context, const FloatRect& rect)
+        : m_context(context)
+        , m_cullApplied(true)
+    {
+        context.beginCull(rect);
+    }
+
+    ~GraphicsContextCullSaver()
+    {
+        if (m_cullApplied)
+            m_context.endCull();
+    }
+
+    void cull(const FloatRect& rect)
+    {
+        ASSERT(!m_cullApplied);
+        m_context.beginCull(rect);
+        m_cullApplied = true;
+    }
+
+private:
+    GraphicsContext& m_context;
+    bool m_cullApplied;
+};
+
+} // namespace WebCore
+
+#endif // GraphicsContextCullSaver_h