Track connected subframes per-Document instead of per-Node.

third_party/WebKit/Source/core/dom/SubframeTracker.h

Index: third_party/WebKit/Source/core/dom/SubframeTracker.h
diff --git a/third_party/WebKit/Source/core/dom/SubframeTracker.h b/third_party/WebKit/Source/core/dom/SubframeTracker.h
new file mode 100644
index 0000000000000000000000000000000000000000..2cd7a9134811f914c56cd4c6fff0f01b343d1030
--- /dev/null
+++ b/third_party/WebKit/Source/core/dom/SubframeTracker.h
@@ -0,0 +1,46 @@
+// Copyright 2016 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 SubframeTracker_h
+#define SubframeTracker_h
+
+#include "platform/heap/Handle.h"
+#include "wtf/Allocator.h"
+#include "wtf/Noncopyable.h"
+
+namespace blink {
+
+class HTMLFrameOwnerElement;
+class Node;
+
+class SubframeTracker final {
+    WTF_MAKE_NONCOPYABLE(SubframeTracker);
+    DISALLOW_NEW();
+public:
+    enum DisconnectPolicy { RootAndDescendants, DescendantsOnly };
+
+    SubframeTracker();
+
+    bool hasConnectedSubframes(Node&) const;
+    void disconnectSubframesAt(Node&, DisconnectPolicy = RootAndDescendants);
+
+    DECLARE_TRACE();
+
+private:
+    friend class HTMLFrameOwnerElement;
+
+    void connectSubframe(HTMLFrameOwnerElement&);
+    void disconnectSubframe(HTMLFrameOwnerElement&);
+
+    // Set of nodes in a Document that have a descendant connected subframe. The
+    // ordering of this set is similar to a pre-order, depth-first traversal of
+    // the DOM tree, though relative traversal of sibling nodes is not
+    // necessarily maintained.
+    using SubframeNodeSet = WillBeHeapListHashSet<RawPtrWillBeMember<Node>>;
+    SubframeNodeSet m_connectedSubframeNodes;
+};
+
+} // namespace blink
+
+#endif // SubframeTracker_h