Don't cache subsequence whose layer is not fully contained by repaint rect

Source/core/paint/DeprecatedPaintLayerPainter.h

Index: Source/core/paint/DeprecatedPaintLayerPainter.h
diff --git a/Source/core/paint/DeprecatedPaintLayerPainter.h b/Source/core/paint/DeprecatedPaintLayerPainter.h
index 9c0fe9f0707ca751ef67b59cee1c2618e09050b1..7e2b27edb04a7754a58fcb5fa8b86871b8a4bf47 100644
--- a/Source/core/paint/DeprecatedPaintLayerPainter.h
+++ b/Source/core/paint/DeprecatedPaintLayerPainter.h
@@ -22,26 +22,36 @@ class CORE_EXPORT DeprecatedPaintLayerPainter {
 public:
     enum FragmentPolicy { AllowMultipleFragments, ForceSingleFragment };
 
+    enum PaintResult {
+        // The layer is fully painted. This includes cases that nothing needs painting
+        // regardless of the paint rect.
+        FullyPainted,
+        // Some part of the layer is out of the paint rect and may be not fully painted.
+        // The results cannot be cached because they may change when paint rect changes.
+        MaybeNotFullyPainted
+    };
+
     DeprecatedPaintLayerPainter(DeprecatedPaintLayer& paintLayer) : m_paintLayer(paintLayer) { }
 
     // The paint() method paints the layers that intersect the damage rect from back to front.
     //  paint() assumes that the caller will clip to the bounds of damageRect if necessary.
     void paint(GraphicsContext*, const LayoutRect& damageRect, const GlobalPaintFlags = GlobalPaintNormalPhase, LayoutObject* paintingRoot = 0, PaintLayerFlags = 0);
     // paintLayer() assumes that the caller will clip to the bounds of the painting dirty if necessary.
-    void paintLayer(GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, PaintLayerFlags);
+    PaintResult paintLayer(GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, PaintLayerFlags);
     // paintLayerContents() assumes that the caller will clip to the bounds of the painting dirty rect if necessary.
-    void paintLayerContents(GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, PaintLayerFlags, FragmentPolicy = AllowMultipleFragments);
+    PaintResult paintLayerContents(GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, PaintLayerFlags, FragmentPolicy = AllowMultipleFragments);
 
     void paintOverlayScrollbars(GraphicsContext*, const LayoutRect& damageRect, const GlobalPaintFlags, LayoutObject* paintingRoot = 0);
 
 private:
     enum ClipState { HasNotClipped, HasClipped };
 
-    void paintLayerContentsAndReflection(GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, PaintLayerFlags, FragmentPolicy = AllowMultipleFragments);
-    void paintLayerWithTransform(GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, PaintLayerFlags);
-    void paintFragmentByApplyingTransform(GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, PaintLayerFlags, const LayoutPoint& fragmentTranslation);
+    PaintResult paintLayerInternal(GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, PaintLayerFlags);
+    PaintResult paintLayerContentsAndReflection(GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, PaintLayerFlags, FragmentPolicy = AllowMultipleFragments);
+    PaintResult paintLayerWithTransform(GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, PaintLayerFlags);
+    PaintResult paintFragmentByApplyingTransform(GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, PaintLayerFlags, const LayoutPoint& fragmentTranslation);
 
-    void paintChildren(unsigned childrenToVisit, GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, PaintLayerFlags);
+    PaintResult paintChildren(unsigned childrenToVisit, GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, PaintLayerFlags);
     bool atLeastOneFragmentIntersectsDamageRect(DeprecatedPaintLayerFragments&, const DeprecatedPaintLayerPaintingInfo&, PaintLayerFlags, const LayoutPoint& offsetFromRoot);
     void paintFragmentWithPhase(PaintPhase, const DeprecatedPaintLayerFragment&, GraphicsContext*, const ClipRect&, const DeprecatedPaintLayerPaintingInfo&, LayoutObject* paintingRootForLayoutObject, PaintLayerFlags, ClipState);
     void paintBackgroundForFragments(const DeprecatedPaintLayerFragments&, GraphicsContext*,