Improve performance of GeometryMapper cache.

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

Index: third_party/WebKit/Source/platform/graphics/paint/ClipPaintPropertyNode.h
diff --git a/third_party/WebKit/Source/platform/graphics/paint/ClipPaintPropertyNode.h b/third_party/WebKit/Source/platform/graphics/paint/ClipPaintPropertyNode.h
index 7749aace88eaec366958ae0a6b16465392c13f75..ba3c3f3dc52dea45af43945a41efe6f38878fd54 100644
--- a/third_party/WebKit/Source/platform/graphics/paint/ClipPaintPropertyNode.h
+++ b/third_party/WebKit/Source/platform/graphics/paint/ClipPaintPropertyNode.h
@@ -7,6 +7,7 @@
 
 #include "platform/PlatformExport.h"
 #include "platform/geometry/FloatRoundedRect.h"
+#include "platform/graphics/paint/FloatClipRect.h"
 #include "platform/graphics/paint/TransformPaintPropertyNode.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
@@ -86,21 +87,60 @@ class PLATFORM_EXPORT ClipPaintPropertyNode
     return m_directCompositingReasons != CompositingReasonNone;
   }
 
+  // Clears all clip caches (see getClipCache()).
+  static void clearCache();
+
+  struct ClipAndTransform {
+    const ClipPaintPropertyNode* ancestorClip;
+    const TransformPaintPropertyNode* ancestorTransform;
+    bool operator==(const ClipAndTransform& other) const {
+      return ancestorClip == other.ancestorClip &&
+             ancestorTransform == other.ancestorTransform;
+    }
+    ClipAndTransform(const ClipPaintPropertyNode* ancestorClipArg,
+                     const TransformPaintPropertyNode* ancestorTransformArg)
+        : ancestorClip(ancestorClipArg),
+          ancestorTransform(ancestorTransformArg) {}
+  };
+
  private:
   ClipPaintPropertyNode(
       PassRefPtr<const ClipPaintPropertyNode> parent,
       PassRefPtr<const TransformPaintPropertyNode> localTransformSpace,
       const FloatRoundedRect& clipRect,
-      CompositingReasons directCompositingReasons)
-      : m_parent(parent),
-        m_localTransformSpace(localTransformSpace),
-        m_clipRect(clipRect),
-        m_directCompositingReasons(directCompositingReasons) {}
+      CompositingReasons directCompositingReasons);
+
+  struct ClipCacheEntry {
+    const ClipAndTransform clipAndTransform;
+    const FloatClipRect clipRect;
+    ClipCacheEntry(const ClipAndTransform& clipAndTransformArg,
+                   const FloatClipRect& clipRectArg)
+        : clipAndTransform(clipAndTransformArg), clipRect(clipRectArg) {}
+  };
+
+  Vector<ClipCacheEntry>* getClipCacheEntries();
+
+  // For access to getCachedClip() and setCachedClip.
+  friend class GeometryMapper;
+  friend class GeometryMapperTest;
+
+  // Returns the "clip visual rect" (See GeometryMapper.h) of |this|
+  // in the space of |ancestors|, if there is one cached. Otherwise returns
+  // null.
+  const FloatClipRect* getCachedClip(const ClipAndTransform& ancestors) const;
+  // Stores the "clip visual rect" of |this in the space of |ancestors|,
+  // into a local cache.
+

[pdr., 2017/03/07 23:25:43]

nit: extra newline

+  void setCachedClip(const ClipAndTransform&, const FloatClipRect&) const;
 
   RefPtr<const ClipPaintPropertyNode> m_parent;
   RefPtr<const TransformPaintPropertyNode> m_localTransformSpace;
   FloatRoundedRect m_clipRect;
   CompositingReasons m_directCompositingReasons;
+
+  std::unique_ptr<Vector<ClipCacheEntry>> m_clipCache;
+  unsigned m_cacheGeneration;
+  const FloatClipRect m_infiniteClip;

[pdr., 2017/03/07 23:25:43]

I don't quite understand this. What is it used for?

 };
 
 // Redeclared here to avoid ODR issues.