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

Source/core/paint/DeprecatedPaintLayerPainter.h

 // Copyright 2014 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 DeprecatedPaintLayerPainter_h
 #define DeprecatedPaintLayerPainter_h
 
 #include "core/CoreExport.h"
 #include "core/paint/DeprecatedPaintLayerFragment.h"
 #include "core/paint/DeprecatedPaintLayerPaintingInfo.h"
 #include "wtf/Allocator.h"
 
 namespace blink {
 
 class ClipRect;
 class DeprecatedPaintLayer;
 class GraphicsContext;
 class LayoutPoint;
 
 class CORE_EXPORT DeprecatedPaintLayerPainter {
     STACK_ALLOCATED();
 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*,
         const LayoutRect& transparencyPaintDirtyRect, const DeprecatedPaintLayerPaintingInfo&, LayoutObject* paintingRootForLayoutObject, PaintLayerFlags);
     void paintForegroundForFragments(const DeprecatedPaintLayerFragments&, GraphicsContext*,
         const LayoutRect& transparencyPaintDirtyRect, const DeprecatedPaintLayerPaintingInfo&, LayoutObject* paintingRootForLayoutObject,
         bool selectionOnly, PaintLayerFlags);
     void paintForegroundForFragmentsWithPhase(PaintPhase, const DeprecatedPaintLayerFragments&, GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, LayoutObject* paintingRootForLayoutObject, PaintLayerFlags, ClipState);
     void paintOutlineForFragments(const DeprecatedPaintLayerFragments&, GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, LayoutObject* paintingRootForLayoutObject, PaintLayerFlags);
     void paintOverflowControlsForFragments(const DeprecatedPaintLayerFragments&, GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, PaintLayerFlags);
     void paintMaskForFragments(const DeprecatedPaintLayerFragments&, GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, LayoutObject* paintingRootForLayoutObject, PaintLayerFlags);
     void paintChildClippingMaskForFragments(const DeprecatedPaintLayerFragments&, GraphicsContext*, const DeprecatedPaintLayerPaintingInfo&, LayoutObject* paintingRootForLayoutObject, PaintLayerFlags);
 
     static bool needsToClip(const DeprecatedPaintLayerPaintingInfo& localPaintingInfo, const ClipRect&);
 
     // Returns whether this layer should be painted during sofware painting (i.e., not via calls from CompositedDeprecatedPaintLayerMapping to draw into composited
     // layers).
     bool shouldPaintLayerInSoftwareMode(const GlobalPaintFlags, PaintLayerFlags paintFlags);
 
     DeprecatedPaintLayer& m_paintLayer;
 };
 
 } // namespace blink
 
 #endif // DeprecatedPaintLayerPainter_h