Oilpan: Introduce TempRangeScope to avoid needless Range attaches on Document.

Source/core/dom/Range.h

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * (C) 2000 Gunnstein Lye (gunnstein@netcom.no)
  * (C) 2000 Frederik Holljen (frederik.holljen@hig.no)
  * (C) 2001 Peter Kelly (pmk@post.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 152 matching lines @@
     static PassRefPtrWillBeRawPtr<Node> processContentsBetweenOffsets(ActionType, PassRefPtrWillBeRawPtr<DocumentFragment>, Node*, unsigned startOffset, unsigned endOffset, ExceptionState&);
     static void processNodes(ActionType, WillBeHeapVector<RefPtrWillBeMember<Node> >&, PassRefPtrWillBeRawPtr<Node> oldContainer, PassRefPtrWillBeRawPtr<Node> newContainer, ExceptionState&);
     enum ContentsProcessDirection { ProcessContentsForward, ProcessContentsBackward };
     static PassRefPtrWillBeRawPtr<Node> processAncestorsAndTheirSiblings(ActionType, Node* container, ContentsProcessDirection, PassRefPtrWillBeRawPtr<Node> clonedContainer, Node* commonRoot, ExceptionState&);
 
     RefPtrWillBeMember<Document> m_ownerDocument; // Cannot be null.
     RangeBoundaryPoint m_start;
     RangeBoundaryPoint m_end;
 };
 
+#if ENABLE(OILPAN)
+// Ranges are registered on the owner document so that they can be
+// updated via the document when the document changes. Ranges are
+// often used as short-lived results of subcomputations that become
+// unreachable without any document modifications. Such short-lived
+// ranges need not be registered with the document. When a
+// TempRangeScope is on the stack created range objects are not
+// attached to the document. With Oilpan this is important to not
+// build up a large set of ranges on the Document that we will waste
+// time updating even though they will never be needed.
+class TempRangeScope {

[haraken, 2014/06/24 11:57:16]

TempRangeScope => TemporaryRangeScope

Blink prefers a fully qualified name.

[Mads Ager (chromium), 2014/06/24 12:16:51]

Done.

+public:
+    TempRangeScope() { ++s_nesting; }
+    ~TempRangeScope() { --s_nesting; }
+    static bool active() { return s_nesting != 0; }
+private:
+    static unsigned s_nesting;
+};
+#else
+class TempRangeScope {
+public:
+    TempRangeScope() { }
+    static bool active() { return false; }
+};
+#endif
+
 PassRefPtrWillBeRawPtr<Range> rangeOfContents(Node*);
 
 bool areRangesEqual(const Range*, const Range*);
 
 } // namespace
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showTree(const WebCore::Range*);
 #endif
 
 #endif