Revert 146726 "AXObjectCache gets recreated during document tear..."

Source/WebCore/editing/mac/FrameSelectionMac.mm

Index: Source/WebCore/editing/mac/FrameSelectionMac.mm
===================================================================
--- Source/WebCore/editing/mac/FrameSelectionMac.mm	(revision 146890)
+++ Source/WebCore/editing/mac/FrameSelectionMac.mm	(working copy)
@@ -49,10 +49,8 @@
 {
     Document* document = m_frame->document();
 
-    if (m_selection.start().isNotNull() && m_selection.end().isNotNull()) {
-        if (AXObjectCache* cache = document->existingAXObjectCache())
-            cache->postNotification(m_selection.start().deprecatedNode()->renderer(), AXObjectCache::AXSelectedTextChanged, false);
-    }
+    if (AXObjectCache::accessibilityEnabled() && m_selection.start().isNotNull() && m_selection.end().isNotNull())
+        document->axObjectCache()->postNotification(m_selection.start().deprecatedNode()->renderer(), AXObjectCache::AXSelectedTextChanged, false);
 
     // if zoom feature is enabled, insertion point changes should update the zoom
     if (!UAZoomEnabled() || !m_selection.isCaret())