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

Source/core/editing/FrameSelection.cpp

 /*
  * Copyright (C) 2004, 2008, 2009, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
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@@ skipping 311 matching lines @@
     if (isNone() || !node.inActiveDocument())
         return;
 
     respondToNodeModification(node, removingNodeRemovesPosition(node, m_selection.base()), removingNodeRemovesPosition(node, m_selection.extent()),
         removingNodeRemovesPosition(node, m_selection.start()), removingNodeRemovesPosition(node, m_selection.end()));
 }
 
 void FrameSelection::respondToNodeModification(Node& node, bool baseRemoved, bool extentRemoved, bool startRemoved, bool endRemoved)
 {
     ASSERT(node.document().isActive());
+    TemporaryRangeScope scope;

[yosin_UTC9, 2014/06/25 01:22:20]

It seems tempoary new Range object is created by |FrameSelection::firstRange()|
when |m_logicalRange| isn't null. But, cloned range is used for comparision. So,
we don't need to actually create new Range object.

We should change this logic to avoid creating Range object rather than using
|TemporaryRangeScope|.

[Mads Ager (chromium), 2014/06/25 11:41:42]

It seems that all the comparison logic is all hidden inside the Range object
abstraction at this point. It is not clear to me if there are other comparison
methods that give me what I need here or how to split out the comparison logic
from the Ranges. 

 
     bool clearRenderTreeSelection = false;
     bool clearDOMTreeSelection = false;
 
     if (startRemoved || endRemoved) {
         Position start = m_selection.start();
         Position end = m_selection.end();
         if (startRemoved)
             updatePositionForNodeRemoval(start, node);
         if (endRemoved)
@@ skipping 1545 matching lines @@
     sel.showTreeForThis();
 }
 
 void showTree(const WebCore::FrameSelection* sel)
 {
     if (sel)
         sel->showTreeForThis();
 }
 
 #endif