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

Source/core/editing/spellcheck/SpellCheckRequester.cpp

Index: Source/core/editing/spellcheck/SpellCheckRequester.cpp
diff --git a/Source/core/editing/spellcheck/SpellCheckRequester.cpp b/Source/core/editing/spellcheck/SpellCheckRequester.cpp
index a5a99b8e2d641440ee7c76e0e59982527298ba69..acdea4597f8967f6609b5699ebd750859fa50932 100644
--- a/Source/core/editing/spellcheck/SpellCheckRequester.cpp
+++ b/Source/core/editing/spellcheck/SpellCheckRequester.cpp
@@ -211,6 +211,17 @@ void SpellCheckRequester::invokeRequest(PassRefPtrWillBeRawPtr<SpellCheckRequest
     client().requestCheckingOfString(m_processingRequest);
 }
 
+void SpellCheckRequester::clearProcessingRequest()
+{
+    // This assumes that m_processingRequest's Ranges aren't shared.
+    if (m_processingRequest->checkingRange())
+        m_processingRequest->checkingRange()->dispose();
+    if (m_processingRequest->paragraphRange())
+        m_processingRequest->paragraphRange()->dispose();
+
+    m_processingRequest.clear();
+}
+
 void SpellCheckRequester::enqueueRequest(PassRefPtrWillBeRawPtr<SpellCheckRequest> request)
 {
     ASSERT(request);
@@ -251,7 +262,7 @@ void SpellCheckRequester::didCheck(int sequence, const Vector<TextCheckingResult
     if (m_lastProcessedSequence < sequence)
         m_lastProcessedSequence = sequence;
 
-    m_processingRequest.clear();
+    clearProcessingRequest();
     if (!m_requestQueue.isEmpty())
         m_timerToProcessQueuedRequest.startOneShot(0, FROM_HERE);
 }