Improve performance of GeometryMapper cache.

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

+// 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.
+
+#include "platform/graphics/paint/GeometryMapperTransformCache.h"
+
+namespace blink {
+
+// All transform caches invalidate themselves by tracking a local cache
+// generation, and invalidating their cache if their cache generation disagrees
+// with s_transformCacheGeneration.
+static unsigned s_transformCacheGeneration = 0;
+
+void GeometryMapperTransformCache::clearCache() {
+  s_transformCacheGeneration++;
+}
+
+Vector<GeometryMapperTransformCache::TransformCacheEntry>*
+GeometryMapperTransformCache::getTransformCacheEntries() {
+  if (m_cacheGeneration != s_transformCacheGeneration || !m_transformCache) {
+    m_transformCache.reset(new Vector<TransformCacheEntry>);
+    m_cacheGeneration = s_transformCacheGeneration;
+  }
+
+  return m_transformCache.get();
+}
+
+const TransformationMatrix* GeometryMapperTransformCache::getCachedTransform(
+    const TransformPaintPropertyNode* ancestorTransform) {
+  auto* transformCacheEntries = getTransformCacheEntries();
+  for (const auto& entry : *transformCacheEntries) {
+    if (entry.ancestorNode == ancestorTransform) {
+      return &entry.toAncestor;
+    }
+  }
+  return nullptr;
+}
+
+void GeometryMapperTransformCache::setCachedTransform(
+    const TransformPaintPropertyNode* ancestorTransform,
+    const TransformationMatrix& matrix) {
+  auto* transformCacheEntries = getTransformCacheEntries();
+#if DCHECK_IS_ON

[pdr., 2017/03/08 02:34:55]

DCHECK_IS_ON()

[chrishtr, 2017/03/08 02:59:28]

Done.

+  for (const auto& entry : transformCacheEntries) {
+    if (entry.ancestorNode == ancestorTransform)
+      DCHECK(false);  // There should be no existing entry.
+  }
+#endif
+  transformCacheEntries->push_back(
+      TransformCacheEntry(ancestorTransform, matrix));
+}
+
+}  // namespace blink