Only store previous clip rects for PaintLayers that support subsequences.

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

Index: third_party/WebKit/Source/core/paint/PrePaintTreeWalk.h
diff --git a/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.h b/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.h
index e57c20b436960a17981447eb7bb4813219c01b54..55fd5f268d1ab98c7247b946ca00f7d96365f6aa 100644
--- a/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.h
+++ b/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.h
@@ -19,7 +19,7 @@ struct PrePaintTreeWalkContext;
 // This class walks the whole layout tree, beginning from the root FrameView,
 // across frame boundaries. Helper classes are called for each tree node to
 // perform actual actions.  It expects to be invoked in InPrePaint phase.
-class PrePaintTreeWalk {
+class CORE_EXPORT PrePaintTreeWalk {

[pdr., 2017/04/12 18:40:06]

Is this only needed for tests?

[chrishtr, 2017/04/13 02:05:59]

Yes.

  public:
   PrePaintTreeWalk() {}
   void Walk(FrameView& root_frame);
@@ -28,6 +28,10 @@ class PrePaintTreeWalk {
   void Walk(FrameView&, const PrePaintTreeWalkContext&);
   void Walk(const LayoutObject&, const PrePaintTreeWalkContext&);
 
+  bool ShouldEarlyOut(const LayoutObject&,
+                      const PrePaintTreeWalkContext& parent_context,
+                      bool& needs_tree_builder_context_update);
+
   // Invalidates paint-layer painting optimizations, such as subsequence caching
   // and empty paint phase optimizations if clips from the context have changed.
   ALWAYS_INLINE void InvalidatePaintLayerOptimizationsIfNeeded(