WIP: prefer using EphemeralRange for SpellChecker.

Source/core/dom/Range.h

Index: Source/core/dom/Range.h
diff --git a/Source/core/dom/Range.h b/Source/core/dom/Range.h
index 9cf22a6fafc1d998f06eb5081dea6bf6e8f43b8c..c5ba37e1a803153a7601da0f071f403bc55310de 100644
--- a/Source/core/dom/Range.h
+++ b/Source/core/dom/Range.h
@@ -64,6 +64,7 @@ public:
 #if !ENABLE(OILPAN) || !defined(NDEBUG)
     ~Range();
 #endif
+    void dispose();

[yosin_UTC9, 2015/09/10 01:58:39]

I'm still in double to introduce |Range::dispose()|. Or, it is too early
to introduce. For spell checker, we don't need to use |dispose()|, since
we can replace all of |Range| usage to |EphmeralRange|.

If we really need to have |Range::dispose()|, let's remove "noop" mark
from |Range:detach()| and use |detach()|.

User script may register "non-needed" |Range| objects to |Document| too.

[sof, 2015/09/10 05:59:02]

Please see 


https://groups.google.com/a/chromium.org/d/msg/oilpan-reviews/bXesw9EnP3Q/Nd7...

for motivation on why dispose() is needed. Rewriting all uses of Range to be
EphemeralRange, if that's possible in the face of tree mutations, isn't a
practical option at this stage.

dispose() is our preferred naming for these operations.

 
     Document& ownerDocument() const { ASSERT(m_ownerDocument); return *m_ownerDocument.get(); }
     Node* startContainer() const { return m_start.container(); }