Improve performance of GeometryMapper cache.

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

+// Copyright 2017 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 GeometryMapperTransformCache_h
+#define GeometryMapperTransformCache_h
+
+#include "platform/PlatformExport.h"
+
+#include "platform/transforms/TransformationMatrix.h"
+#include "wtf/Vector.h"
+
+namespace blink {
+
+class TransformPaintPropertyNode;
+
+// A GeometryMapperTransformCache hangs off a TransformPaintPropertyNode. It
+// stores cached "transformed rects" (See GeometryMapper.h) from that node in
+// ancestor spaces.
+class PLATFORM_EXPORT GeometryMapperTransformCache {
+ public:
+  // 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);
+
+  // Stores the "transformed rect" of |this| in the space of |ancestors|,
+  // into a local cache.
+  void setCachedTransform(const TransformPaintPropertyNode* ancestorTransform,
+                          const TransformationMatrix& toAncestor);
+
+  static void clearCache();
+
+ private:
+  struct TransformCacheEntry {
+    const TransformPaintPropertyNode* ancestorNode;
+    TransformationMatrix toAncestor;
+    TransformCacheEntry(const TransformPaintPropertyNode* ancestorNodeArg,
+                        const TransformationMatrix& toAncestorArg)
+        : ancestorNode(ancestorNodeArg), toAncestor(toAncestorArg) {}
+  };
+
+  Vector<TransformCacheEntry>* getTransformCacheEntries();
+
+  std::unique_ptr<Vector<TransformCacheEntry>> m_transformCache;
+  unsigned m_cacheGeneration;
+};
+
+}  // namespace blink
+
+#endif  // GeometryMapperTransformCache_h