Improve performance of GeometryMapper cache.

third_party/WebKit/Source/platform/graphics/paint/GeometryMapperClipCache.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/GeometryMapperClipCache.h"
+
+#include "platform/graphics/paint/FloatClipRect.h"
+
+namespace blink {
+
+// All clip caches invalidate themselves by tracking a local cache generation,
+// and invalidating their cache if their cache generation disagrees with
+// s_clipCacheGeneration.
+static unsigned s_clipCacheGeneration = 0;
+
+void GeometryMapperClipCache::clearCache() {
+  s_clipCacheGeneration++;
+}
+
+Vector<GeometryMapperClipCache::ClipCacheEntry>*
+GeometryMapperClipCache::getClipCacheEntries() {
+  if (m_cacheGeneration != s_clipCacheGeneration || !m_clipCache) {
+    m_clipCache.reset(new Vector<ClipCacheEntry>);
+    m_cacheGeneration = s_clipCacheGeneration;
+  }
+
+  return m_clipCache.get();
+}
+
+const FloatClipRect* GeometryMapperClipCache::getCachedClip(
+    const ClipAndTransform& clipAndTransform) {
+  auto* clipCacheEntries =
+      const_cast<GeometryMapperClipCache*>(this)->getClipCacheEntries();
+  for (const auto& entry : *clipCacheEntries) {
+    if (entry.clipAndTransform == clipAndTransform) {
+      return &entry.clipRect;
+    }
+  }
+  return nullptr;
+}
+
+void GeometryMapperClipCache::setCachedClip(
+    const ClipAndTransform& clipAndTransform,
+    const FloatClipRect& clip) {
+  auto* clipCacheEntries =
+      const_cast<GeometryMapperClipCache*>(this)->getClipCacheEntries();
+#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 : clipCachEntries) {
+    if (entry.clipAndTransform == clipAndTransform)
+      DCHECK(false);  // There should be no existing entry.
+  }
+#endif
+  clipCacheEntries->push_back(ClipCacheEntry(clipAndTransform, clip));
+}
+
+}  // namespace blink