Introduce Range::dispose() for prompt detachment from owner Document.

Source/core/dom/Range.cpp

Index: Source/core/dom/Range.cpp
diff --git a/Source/core/dom/Range.cpp b/Source/core/dom/Range.cpp
index 4fa8b8b9c967ac96e518ae08f00915e822a667e9..0dad7073402860febc75e698ceb6fe87a146a749 100644
--- a/Source/core/dom/Range.cpp
+++ b/Source/core/dom/Range.cpp
@@ -135,6 +135,14 @@ Range::~Range()
 }
 #endif
 
+void Range::dispose()
+{
+#if ENABLE(OILPAN)
+    // A prompt detach from the owning Document helps avoid GC overhead.
+    m_ownerDocument->detachRange(this);
+#endif
+}
+
 void Range::setDocument(Document& document)
 {
     ASSERT(m_ownerDocument != document);