Improve performance of GeometryMapper cache.

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

Index: third_party/WebKit/Source/platform/graphics/paint/GeometryMapperClipCache.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/paint/GeometryMapperClipCache.cpp b/third_party/WebKit/Source/platform/graphics/paint/GeometryMapperClipCache.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..5dd8982781fbfb34038b7f1f2a716afafc92277a
--- /dev/null
+++ b/third_party/WebKit/Source/platform/graphics/paint/GeometryMapperClipCache.cpp
@@ -0,0 +1,54 @@
+// 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;
+
+GeometryMapperClipCache::GeometryMapperClipCache()
+    : m_cacheGeneration(s_clipCacheGeneration) {}
+
+void GeometryMapperClipCache::clearCache() {
+  s_clipCacheGeneration++;
+}
+
+void GeometryMapperClipCache::invalidateCacheIfNeeded() {
+  if (m_cacheGeneration != s_clipCacheGeneration) {
+    m_clipCache.clear();
+    m_cacheGeneration = s_clipCacheGeneration;
+  }
+}
+
+const FloatClipRect* GeometryMapperClipCache::getCachedClip(
+    const ClipAndTransform& clipAndTransform) {
+  invalidateCacheIfNeeded();
+  for (const auto& entry : m_clipCache) {
+    if (entry.clipAndTransform == clipAndTransform) {
+      return &entry.clipRect;
+    }
+  }
+  return nullptr;
+}
+
+void GeometryMapperClipCache::setCachedClip(
+    const ClipAndTransform& clipAndTransform,
+    const FloatClipRect& clip) {
+  invalidateCacheIfNeeded();
+#if DCHECK_IS_ON()
+  for (const auto& entry : m_clipCache) {
+    if (entry.clipAndTransform == clipAndTransform)
+      DCHECK(false);  // There should be no existing entry.
+  }
+#endif
+  m_clipCache.push_back(ClipCacheEntry(clipAndTransform, clip));
+}
+
+}  // namespace blink