--- a/accessible/base/EventTree.cpp
+++ b/accessible/base/EventTree.cpp
@@ -31,62 +31,20 @@ TreeMutation::TreeMutation(Accessible* a
 
 #ifdef A11Y_LOG
   if (mEventTree != kNoEventTree && logging::IsEnabled(logging::eEventTree)) {
     logging::MsgBegin("EVENTS_TREE", "reordering tree before");
     logging::AccessibleInfo("reordering for", mParent);
     Controller()->RootEventTree().Log();
     logging::MsgEnd();
 
-    logging::MsgBegin("EVENTS_TREE", "Container tree");
     if (logging::IsEnabled(logging::eVerbose)) {
-      nsAutoString level;
-      Accessible* root = mParent->Document();
-      do {
-        const char* prefix = "";
-        if (mParent == root) {
-          prefix = "_X_";
-        }
-        else {
-          const EventTree& ret = Controller()->RootEventTree();
-          if (ret.Find(root)) {
-            prefix = "_с_";
-          }
-        }
-
-        printf("%s", NS_ConvertUTF16toUTF8(level).get());
-        logging::AccessibleInfo(prefix, root);
-        if (root->FirstChild() && !root->FirstChild()->IsDoc()) {
-          level.Append(NS_LITERAL_STRING("  "));
-          root = root->FirstChild();
-          continue;
-        }
-        int32_t idxInParent = root->mParent ?
-          root->mParent->mChildren.IndexOf(root) : -1;
-        if (idxInParent != -1 &&
-            idxInParent < static_cast<int32_t>(root->mParent->mChildren.Length() - 1)) {
-          root = root->mParent->mChildren.ElementAt(idxInParent + 1);
-          continue;
-        }
-
-        while ((root = root->Parent()) && !root->IsDoc()) {
-          level.Cut(0, 2);
-
-          int32_t idxInParent = root->mParent ?
-          root->mParent->mChildren.IndexOf(root) : -1;
-          if (idxInParent != -1 &&
-              idxInParent < static_cast<int32_t>(root->mParent->mChildren.Length() - 1)) {
-            root = root->mParent->mChildren.ElementAt(idxInParent + 1);
-            break;
-          }
-        }
-      }
-      while (root && !root->IsDoc());
+      logging::Tree("EVENTS_TREE", "Container tree", mParent->Document(),
+                    PrefixLog, static_cast<void*>(this));
     }
-    logging::MsgEnd();
   }
 #endif
 
   mParent->mStateFlags |= Accessible::eKidsMutating;
 }
 
 TreeMutation::~TreeMutation()
 {
@@ -168,16 +126,32 @@ TreeMutation::Done()
     logging::MsgBegin("EVENTS_TREE", "reordering tree after");
     logging::AccessibleInfo("reordering for", mParent);
     Controller()->RootEventTree().Log();
     logging::MsgEnd();
   }
 #endif
 }
 
+#ifdef A11Y_LOG
+const char*
+TreeMutation::PrefixLog(void* aData, Accessible* aAcc)
+{
+  TreeMutation* thisObj = reinterpret_cast<TreeMutation*>(aData);
+  if (thisObj->mParent == aAcc) {
+    return "_X_";
+  }
+  const EventTree& ret = thisObj->Controller()->RootEventTree();
+  if (ret.Find(aAcc)) {
+    return "_с_";
+  }
+  return "";
+}
+#endif
+
 
 ////////////////////////////////////////////////////////////////////////////////
 // EventTree
 
 void
 EventTree::Process(const RefPtr<DocAccessible>& aDeathGrip)
 {
   while (mFirst) {

--- a/accessible/base/EventTree.h
+++ b/accessible/base/EventTree.h
@@ -34,16 +34,20 @@ public:
   void Done();
 
 private:
   NotificationController* Controller() const
     { return mParent->Document()->Controller(); }
 
   static EventTree* const kNoEventTree;
 
+#ifdef A11Y_LOG
+  static const char* PrefixLog(void* aData, Accessible*);
+#endif
+
   Accessible* mParent;
   uint32_t mStartIdx;
   uint32_t mStateFlagsCopy;
   EventTree* mEventTree;
 
 #ifdef DEBUG
   bool mIsDone;
 #endif

--- a/accessible/base/Logging.cpp
+++ b/accessible/base/Logging.cpp
@@ -669,16 +669,57 @@ logging::TreeInfo(const char* aMsg, uint
     for (uint32_t idx = 0; idx < aParent->ChildCount(); idx++) {
       AccessibleInfo("child", aParent->GetChildAt(idx));
     }
     MsgEnd();
   }
 }
 
 void
+logging::Tree(const char* aTitle, const char* aMsgText,
+              DocAccessible* aDocument, GetTreePrefix aPrefixFunc,
+              void* aGetTreePrefixData)
+{
+  logging::MsgBegin(aTitle, aMsgText);
+
+  nsAutoString level;
+  Accessible* root = aDocument;
+  do {
+    const char* prefix = aPrefixFunc ? aPrefixFunc(aGetTreePrefixData, root) : "";
+    printf("%s", NS_ConvertUTF16toUTF8(level).get());
+    logging::AccessibleInfo(prefix, root);
+    if (root->FirstChild() && !root->FirstChild()->IsDoc()) {
+      level.Append(NS_LITERAL_STRING("  "));
+      root = root->FirstChild();
+      continue;
+    }
+    int32_t idxInParent = !root->IsDoc() && root->mParent ?
+      root->mParent->mChildren.IndexOf(root) : -1;
+    if (idxInParent != -1 &&
+        idxInParent < static_cast<int32_t>(root->mParent->mChildren.Length() - 1)) {
+      root = root->mParent->mChildren.ElementAt(idxInParent + 1);
+      continue;
+    }
+    while (!root->IsDoc() && (root = root->Parent())) {
+      level.Cut(0, 2);
+      int32_t idxInParent = !root->IsDoc() && root->mParent ?
+        root->mParent->mChildren.IndexOf(root) : -1;
+      if (idxInParent != -1 &&
+          idxInParent < static_cast<int32_t>(root->mParent->mChildren.Length() - 1)) {
+        root = root->mParent->mChildren.ElementAt(idxInParent + 1);
+        break;
+      }
+    }
+  }
+  while (root && !root->IsDoc());
+
+  logging::MsgEnd();
+}
+
+void
 logging::MsgBegin(const char* aTitle, const char* aMsgText, ...)
 {
   printf("\nA11Y %s: ", aTitle);
 
   va_list argptr;
   va_start(argptr, aMsgText);
   vprintf(aMsgText, argptr);
   va_end(argptr);

--- a/accessible/base/Logging.h
+++ b/accessible/base/Logging.h
@@ -135,16 +135,23 @@ void SelChange(nsISelection* aSelection,
  */
 void TreeInfo(const char* aMsg, uint32_t aExtraFlags, ...);
 void TreeInfo(const char* aMsg, uint32_t aExtraFlags,
               const char* aMsg1, Accessible* aAcc,
               const char* aMsg2, nsINode* aNode);
 void TreeInfo(const char* aMsg, uint32_t aExtraFlags, Accessible* aParent);
 
 /**
+ * Log the accessible tree.
+ */
+typedef const char* (*GetTreePrefix)(void* aData, Accessible*);
+void Tree(const char* aTitle, const char* aMsgText, DocAccessible* aDoc,
+          GetTreePrefix aPrefixFunc = nullptr, void* aGetTreePrefixData = nullptr);
+
+/**
  * Log the message ('title: text' format) on new line. Print the start and end
  * boundaries of the message body designated by '{' and '}' (2 spaces indent for
  * body).
  */
 void MsgBegin(const char* aTitle, const char* aMsgText, ...);
 void MsgEnd();
 
 /**

--- a/accessible/generic/Accessible.h
+++ b/accessible/generic/Accessible.h
@@ -45,16 +45,24 @@ class ProxyAccessible;
 class Relation;
 class RootAccessible;
 class TableAccessible;
 class TableCellAccessible;
 class TextLeafAccessible;
 class XULLabelAccessible;
 class XULTreeAccessible;
 
+#ifdef A11Y_LOG
+namespace logging {
+  typedef const char* (*GetTreePrefix)(void* aData, Accessible*);
+  void Tree(const char* aTitle, const char* aMsgText, DocAccessible* aDoc,
+            GetTreePrefix aPrefixFunc, void* GetTreePrefixData);
+};
+#endif
+
 /**
  * Name type flags.
  */
 enum ENameValueFlag {
   /**
    * Name either
    *  a) present (not empty): !name.IsEmpty()
    *  b) no name (was missed): name.IsVoid()
@@ -1115,16 +1123,22 @@ protected:
    */
   uint32_t mStateFlags : kStateFlagsBits;
   uint32_t mContextFlags : kContextFlagsBits;
   uint32_t mType : kTypeBits;
   uint32_t mGenericTypes : kGenericTypesBits;
 
   void StaticAsserts() const;
 
+#ifdef A11Y_LOG
+  friend void logging::Tree(const char* aTitle, const char* aMsgText,
+                            DocAccessible* aDoc,
+                            logging::GetTreePrefix aPrefixFunc,
+                            void* aGetTreePrefixData);
+#endif
   friend class DocAccessible;
   friend class xpcAccessible;
   friend class TreeMutation;
 
   nsAutoPtr<mozilla::a11y::EmbeddedObjCollector> mEmbeddedObjCollector;
   union {
     int32_t mIndexOfEmbeddedChild;
     uint32_t mProxyInterfaces;