Defer pushing the parent stack in recalcStyle until StyleResolver::styleForElement()

Source/core/css/resolver/StyleResolverParentScope.h

Index: Source/core/css/resolver/StyleResolverParentScope.h
diff --git a/Source/core/css/resolver/StyleResolverParentScope.h b/Source/core/css/resolver/StyleResolverParentScope.h
new file mode 100644
index 0000000000000000000000000000000000000000..671250052f6cbbc57dae7eaf9c8c575ca89723dd
--- /dev/null
+++ b/Source/core/css/resolver/StyleResolverParentScope.h
@@ -0,0 +1,91 @@
+/*
+ * Copyright (C) 2013 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef StyleResolverParentScope_h
+#define StyleResolverParentScope_h
+
+#include "core/css/resolver/StyleResolver.h"
+#include "core/dom/Element.h"
+
+namespace WebCore {
+
+// Maintains the parent element stack (and bloom filter) inside recalcStyle.
+class StyleResolverParentScope FINAL {
+public:
+    explicit StyleResolverParentScope(Element& parent);
+    ~StyleResolverParentScope();
+
+    static void pushScopes();
+
+private:
+    void pushParentIfNeeded();
+
+    Element& m_parent;
+    bool m_pushed;
+    StyleResolverParentScope* m_previous;
+
+    static StyleResolverParentScope* s_currentScope;
+};
+
+inline StyleResolverParentScope::StyleResolverParentScope(Element& parent)
+    : m_parent(parent)
+    , m_pushed(false)
+    , m_previous(s_currentScope)
+{
+    ASSERT(m_parent.document().inStyleRecalc());
+    s_currentScope = this;
+}
+
+inline StyleResolverParentScope::~StyleResolverParentScope()
+{
+    if (m_pushed)
+        m_parent.document().styleResolver()->popParentElement(m_parent);
+    s_currentScope = m_previous;
+}
+
+inline void StyleResolverParentScope::pushScopes()
+{
+    if (s_currentScope)
+        s_currentScope->pushParentIfNeeded();
+}
+
+inline void StyleResolverParentScope::pushParentIfNeeded()
+{
+    if (m_pushed)
+        return;
+    if (m_previous)
+        m_previous->pushParentIfNeeded();
+    m_parent.document().styleResolver()->pushParentElement(m_parent);
+    m_pushed = true;
+}
+
+} // namespace WebCore
+
+#endif // StyleResolverParentScope_h