Factor the style invalidation tree walk out of RuleFeatureSet, and make it generic.

Source/core/css/invalidation/StyleInvalidationTreeWalk.h

Index: Source/core/css/invalidation/StyleInvalidationTreeWalk.h
diff --git a/Source/core/css/invalidation/StyleInvalidationTreeWalk.h b/Source/core/css/invalidation/StyleInvalidationTreeWalk.h
new file mode 100644
index 0000000000000000000000000000000000000000..5098565f2fc890b7c0c78a0008ed4995c230caf7
--- /dev/null
+++ b/Source/core/css/invalidation/StyleInvalidationTreeWalk.h
@@ -0,0 +1,63 @@
+// Copyright 2014 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 StyleInvalidationTreeWalk_h
+#define StyleInvalidationTreeWalk_h
+
+#include "core/css/RuleFeature.h"
+
+namespace WebCore {
+
+class StyleInvalidationTreeWalk {
+public:
+    static void computeStyleInvalidation(Document&, RuleFeatureSet*);

[esprehn, 2014/03/19 22:09:04]

No static, this should work like the ChildInsertionNotifier or the
SharedStyleFinder.

StyleInvalidator(document).invalidate();

There's no reason to pass in a RuleFeatureSet, you can get it from the document.

[chrishtr, 2014/03/19 22:49:39]

The point of the static is to enforce invalidator object lifetime to be within
the execution time of calls to computeStyleInvalidation(), which in turn
enforces that the recursion data is correctly initialized and the object can't
be run twice. This is the main reason I made a class for the tree walk.

[esprehn, 2014/03/19 23:04:14]

That's not the correct way to solve this. We have lots of these objects. If
you're really paranoid use STACK_ALLOCATED().

This code should match the style of the rest of the engine.

[chrishtr, 2014/03/20 00:08:35]

Matching style is good. Done.

+
+private:
+    StyleInvalidationTreeWalk(const RuleFeatureSet*);
+
+    bool invalidateStyle(Element*);
+    bool invalidateStyleForChildren(Element*);
+
+    bool checkInvalidationSetsAgainstElement(Element*);

[esprehn, 2014/03/19 22:09:04]

These should all be references.

[chrishtr, 2014/03/19 22:49:39]

Done.

+
+    class RecursionCheckpoint;
+    class RecursionData {
+    public:
+        RecursionData() : m_foundInvalidationSet(false) { }
+        void pushInvalidationSet(const DescendantInvalidationSet&);
+        bool matchesCurrentInvalidationSets(Element*);
+        bool foundInvalidationSet() { return m_foundInvalidationSet; }
+
+    private:
+        Vector<AtomicString> m_invalidationClasses;
+        bool m_foundInvalidationSet;
+        friend class RecursionCheckpoint;

[esprehn, 2014/03/19 22:09:04]

No friends please.

[chrishtr, 2014/03/19 22:49:39]

Done.

+    };
+
+    class RecursionCheckpoint {
+    public:
+        RecursionCheckpoint(RecursionData* data)
+            : m_prevClassLength(data->m_invalidationClasses.size()),
+            m_prevFoundInvalidationSet(data->m_foundInvalidationSet),
+            m_data(data)
+        { }
+        ~RecursionCheckpoint()
+        {
+            m_data->m_invalidationClasses.remove(m_prevClassLength, m_data->m_invalidationClasses.size() - m_prevClassLength);
+            m_data->m_foundInvalidationSet = m_prevFoundInvalidationSet;
+        }
+
+    private:
+        int m_prevClassLength;
+        bool m_prevFoundInvalidationSet;
+        RecursionData* m_data;
+    };
+
+    const RuleFeatureSet* m_featureSet;
+    RecursionData m_recursionData;
+};
+
+} // namespace WebCore
+
+#endif // StyleInvalidationTreeWalk_h