Add support for flattening in GeometryMapper.

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:
   GeometryMapperTransformCache();
 
   // Returns the transformed rect (see GeometryMapper.h) of |this| in the
   // space of |ancestorTransform|, if there is one cached. Otherwise returns
   // null.
+  //
+  // These transforms are not flattened to 2d, even if the ancestor transform
+  // space flattens.
   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();
 
@@ skipping 10 matching lines @@
 
   Vector<TransformCacheEntry> m_transformCache;
   unsigned m_cacheGeneration;
 
   DISALLOW_COPY_AND_ASSIGN(GeometryMapperTransformCache);
 };
 
 }  // namespace blink
 
 #endif  // GeometryMapperTransformCache_h