First step of PaintInvalidator implementation

third_party/WebKit/Source/core/paint/BoxPaintInvalidator.h

+// Copyright 2016 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.
+
+#ifndef BoxPaintInvalidator_h
+#define BoxPaintInvalidator_h
+
+#include "platform/graphics/PaintInvalidationReason.h"
+#include "wtf/Allocator.h"
+
+namespace blink {
+
+class LayoutBox;
+class LayoutRect;
+class LayoutSize;
+struct PaintInvalidatorContext;
+
+class BoxPaintInvalidator {
+    STACK_ALLOCATED();
+public:
+    BoxPaintInvalidator(const LayoutBox& box, const PaintInvalidatorContext& context)
+        : m_box(box), m_context(context) { }
+
+    static void boxWillBeDestroyed(const LayoutBox&);
+
+    PaintInvalidationReason invalidatePaintIfNeeded();
+
+private:
+    PaintInvalidationReason computePaintInvalidationReason();
+
+    void incrementallyInvalidatePaint();
+    void invalidatePaintRectClippedByOldAndNewBounds(const LayoutRect&);
+
+    bool needsToSavePreviousBoxSizes();
+    void savePreviousBoxSizesIfNeeded();
+    LayoutSize computePreviousBorderBoxSize(const LayoutSize& previousBoundsSize);
+
+    const LayoutBox& m_box;
+    const PaintInvalidatorContext& m_context;
+};
+
+} // namespace blink
+
+#endif