Improve performance of GeometryMapper cache.

third_party/WebKit/Source/platform/graphics/paint/TransformPaintPropertyNode.h

 // Copyright 2015 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 TransformPaintPropertyNode_h
 #define TransformPaintPropertyNode_h
 
 #include "platform/PlatformExport.h"
 #include "platform/geometry/FloatPoint3D.h"
 #include "platform/graphics/CompositingReasons.h"
@@ skipping 170 matching lines @@
            m_directCompositingReasons == o.m_directCompositingReasons &&
            m_compositorElementId == o.m_compositorElementId &&
            !!m_scroll == !!o.m_scroll;
   }
 
   String toTreeString() const;
 #endif
 
   String toString() const;
 
+  // Clears all transform caches (see getTransformCache()).
+  static void clearCache();
+
  private:
   TransformPaintPropertyNode(
       PassRefPtr<const TransformPaintPropertyNode> parent,
       const TransformationMatrix& matrix,
       const FloatPoint3D& origin,
       bool flattensInheritedTransform,
       unsigned renderingContextId,
       CompositingReasons directCompositingReasons,
       CompositorElementId compositorElementId,
       PassRefPtr<ScrollPaintPropertyNode> scroll = nullptr)
       : m_parent(parent),
         m_matrix(matrix),
         m_origin(origin),
         m_flattensInheritedTransform(flattensInheritedTransform),
         m_renderingContextId(renderingContextId),
         m_directCompositingReasons(directCompositingReasons),
         m_compositorElementId(compositorElementId),
         m_scroll(scroll) {}
 
+  struct TransformCacheEntry {
+    const TransformPaintPropertyNode* ancestorNode;
+    TransformationMatrix toAncestor;
+    TransformCacheEntry(const TransformPaintPropertyNode* ancestorNodeArg,
+                        const TransformationMatrix& toAncestorArg)
+        : ancestorNode(ancestorNodeArg), toAncestor(toAncestorArg) {}
+  };
+
+  // For access to getCachedTransform() and setCachedTransform.
+  friend class GeometryMapper;
+  friend class GeometryMapperTest;
+
+  Vector<TransformCacheEntry>* getTransformCacheEntries();
+
+  // Returns the "transformed rect" (see GeometryMapper.h) of |this| in the
+  // space of |ancestorTransform|, if there is one cached. Otherwise returns
+  // null.
+  const TransformationMatrix* getCachedTransform(
+      const TransformPaintPropertyNode* ancestorTransform) const;
+
+  // Stores the "transformed rect" of |this| in the space of |ancestors|,
+  // into a local cache.
+  void setCachedTransform(const TransformPaintPropertyNode* ancestorTransform,
+                          const TransformationMatrix& toAncestor) const;
+
   RefPtr<const TransformPaintPropertyNode> m_parent;
   TransformationMatrix m_matrix;
   FloatPoint3D m_origin;
   bool m_flattensInheritedTransform;
   unsigned m_renderingContextId;
   CompositingReasons m_directCompositingReasons;
   CompositorElementId m_compositorElementId;
   RefPtr<ScrollPaintPropertyNode> m_scroll;
+
+  std::unique_ptr<Vector<TransformCacheEntry>> m_transformCache;
+  unsigned m_cacheGeneration;
 };
 
 // Redeclared here to avoid ODR issues.
 // See platform/testing/PaintPrinters.h.
 void PrintTo(const TransformPaintPropertyNode&, std::ostream*);
 
 }  // namespace blink
 
 #endif  // TransformPaintPropertyNode_h