--- a/widget/windows/TSFTextStore.cpp
+++ b/widget/windows/TSFTextStore.cpp
@@ -1975,21 +1975,21 @@ TSFTextStore::GetSelection(ULONG ulIndex
   if (ulIndex != static_cast<ULONG>(TS_DEFAULT_SELECTION) &&
       ulIndex != 0) {
     MOZ_LOG(sTextStoreLog, LogLevel::Error,
            ("TSF: 0x%p   TSFTextStore::GetSelection() FAILED due to "
             "unsupported selection", this));
     return TS_E_NOSELECTION;
   }
 
-  Selection& currentSel = CurrentSelection();
+  Selection& currentSel = SelectionForTSFRef();
   if (currentSel.IsDirty()) {
     MOZ_LOG(sTextStoreLog, LogLevel::Error,
            ("TSF: 0x%p   TSFTextStore::GetSelection() FAILED due to "
-            "CurrentSelection() failure", this));
+            "SelectionForTSFRef() failure", this));
     return E_FAIL;
   }
   *pSelection = currentSel.ACP();
   *pcFetched = 1;
   MOZ_LOG(sTextStoreLog, LogLevel::Info,
          ("TSF: 0x%p   TSFTextStore::GetSelection() succeeded", this));
   return S_OK;
 }
@@ -2017,21 +2017,21 @@ TSFTextStore::ContentForTSFRef()
             "called wrong timing, IsReadLocked()=%s, "
             "mContentForTSF.IsInitialized()=%s",
             this, GetBoolName(IsReadLocked()),
             GetBoolName(mContentForTSF.IsInitialized())));
     mContentForTSF.Clear();
     return mContentForTSF;
   }
 
-  Selection& currentSel = CurrentSelection();
+  Selection& currentSel = SelectionForTSFRef();
   if (currentSel.IsDirty()) {
     MOZ_LOG(sTextStoreLog, LogLevel::Error,
            ("TSF: 0x%p   TSFTextStore::ContentForTSFRef(), FAILED, due to "
-            "CurrentSelection() failure", this));
+            "SelectionForTSFRef() failure", this));
     mContentForTSF.Clear();
     return mContentForTSF;
   }
 
   if (!mContentForTSF.IsInitialized()) {
     nsAutoString text;
     if (NS_WARN_IF(!GetCurrentText(text))) {
       MOZ_LOG(sTextStoreLog, LogLevel::Error,
@@ -2092,17 +2092,17 @@ TSFTextStore::GetCurrentText(nsAString& 
     return false;
   }
 
   aTextContent = queryText.mReply.mString;
   return true;
 }
 
 TSFTextStore::Selection&
-TSFTextStore::CurrentSelection()
+TSFTextStore::SelectionForTSFRef()
 {
   if (mSelectionForTSF.IsDirty()) {
     MOZ_ASSERT(!mDestroyed);
     // If the window has never been available, we should crash since working
     // with broken values may make TIP confused.
     if (!mWidget || mWidget->Destroyed()) {
       MOZ_CRASH();
     }
@@ -2116,17 +2116,17 @@ TSFTextStore::CurrentSelection()
 
     mSelectionForTSF.SetSelection(querySelection.mReply.mOffset,
                                   querySelection.mReply.mString.Length(),
                                   querySelection.mReply.mReversed,
                                   querySelection.GetWritingMode());
   }
 
   MOZ_LOG(sTextStoreLog, LogLevel::Debug,
-         ("TSF: 0x%p   TSFTextStore::CurrentSelection(): "
+         ("TSF: 0x%p   TSFTextStore::SelectionForTSFRef(): "
           "acpStart=%d, acpEnd=%d (length=%d), reverted=%s",
           this, mSelectionForTSF.StartOffset(), mSelectionForTSF.EndOffset(),
           mSelectionForTSF.Length(),
           GetBoolName(mSelectionForTSF.IsReversed())));
 
   return mSelectionForTSF;
 }
 
@@ -2292,17 +2292,17 @@ TSFTextStore::RestartCompositionIfNecess
           this));
   return S_OK;
 }
 
 HRESULT
 TSFTextStore::RestartComposition(ITfCompositionView* aCompositionView,
                                  ITfRange* aNewRange)
 {
-  Selection& currentSelection = CurrentSelection();
+  Selection& currentSelection = SelectionForTSFRef();
 
   LONG newStart, newLength;
   HRESULT hr = GetRangeExtent(aNewRange, &newStart, &newLength);
   LONG newEnd = newStart + newLength;
 
   MOZ_LOG(sTextStoreLog, LogLevel::Debug,
          ("TSF: 0x%p   TSFTextStore::RestartComposition(aCompositionView=0x%p, "
           "aNewRange=0x%p { newStart=%d, newLength=%d }), "
@@ -2311,17 +2311,17 @@ TSFTextStore::RestartComposition(ITfComp
           this, aCompositionView, aNewRange, newStart, newLength,
           mComposition.mStart, mComposition.mString.Length(),
           GetBoolName(currentSelection.IsDirty()),
           currentSelection.StartOffset(), currentSelection.Length()));
 
   if (currentSelection.IsDirty()) {
     MOZ_LOG(sTextStoreLog, LogLevel::Error,
            ("TSF: 0x%p   TSFTextStore::RestartComposition() FAILED "
-            "due to CurrentSelection() failure", this));
+            "due to SelectionForTSFRef() failure", this));
     return E_FAIL;
   }
 
   if (FAILED(hr)) {
     MOZ_LOG(sTextStoreLog, LogLevel::Error,
            ("TSF: 0x%p   TSFTextStore::RestartComposition() FAILED "
             "due to GetRangeExtent() failure", this));
     return hr;
@@ -2497,21 +2497,21 @@ TSFTextStore::RecordCompositionUpdateAct
   if (FAILED(hr) || !enumRanges) {
     MOZ_LOG(sTextStoreLog, LogLevel::Error,
            ("TSF: 0x%p   TSFTextStore::RecordCompositionUpdateAction() FAILED "
             "due to attrPropetry->EnumRanges() failure", this));
     return FAILED(hr) ? hr : E_FAIL;
   }
 
   // First, put the log of content and selection here.
-  Selection& currentSel = CurrentSelection();
+  Selection& currentSel = SelectionForTSFRef();
   if (currentSel.IsDirty()) {
     MOZ_LOG(sTextStoreLog, LogLevel::Error,
            ("TSF: 0x%p   TSFTextStore::RecordCompositionUpdateAction() FAILED "
-            "due to CurrentSelection() failure", this));
+            "due to SelectionForTSFRef() failure", this));
     return E_FAIL;
   }
 
   PendingAction* action = LastOrNewPendingCompositionUpdate();
   action->mData = mComposition.mString;
   // The ranges might already have been initialized, however, if this is
   // called again, that means we need to overwrite the ranges with current
   // information.
@@ -2659,21 +2659,21 @@ TSFTextStore::SetSelectionInternal(const
           this, pSelection->acpStart, pSelection->acpEnd,
           GetActiveSelEndName(pSelection->style.ase),
           GetBoolName(pSelection->style.fInterimChar),
           GetBoolName(aDispatchCompositionChangeEvent),
           GetBoolName(mComposition.IsComposing())));
 
   MOZ_ASSERT(IsReadWriteLocked());
 
-  Selection& currentSel = CurrentSelection();
+  Selection& currentSel = SelectionForTSFRef();
   if (currentSel.IsDirty()) {
     MOZ_LOG(sTextStoreLog, LogLevel::Error,
        ("TSF: 0x%p   TSFTextStore::SetSelectionInternal() FAILED due to "
-        "CurrentSelection() failure", this));
+        "SelectionForTSFRef() failure", this));
     return E_FAIL;
   }
 
   // If actually the range is not changing, we should do nothing.
   // Perhaps, we can ignore the difference change because it must not be
   // important for following edit.
   if (currentSel.EqualsExceptDirection(*pSelection)) {
     MOZ_LOG(sTextStoreLog, LogLevel::Error,
@@ -3264,25 +3264,25 @@ TSFTextStore::RetrieveRequestedAttrs(ULO
       switch (i) {
         case eInputScope: {
           paAttrVals[count].varValue.vt = VT_UNKNOWN;
           RefPtr<IUnknown> inputScope = new InputScopeImpl(mInputScopes);
           paAttrVals[count].varValue.punkVal = inputScope.forget().take();
           break;
         }
         case eTextVerticalWriting: {
-          Selection& currentSelection = CurrentSelection();
+          Selection& currentSelection = SelectionForTSFRef();
           paAttrVals[count].varValue.vt = VT_BOOL;
           paAttrVals[count].varValue.boolVal =
             currentSelection.GetWritingMode().IsVertical()
             ? VARIANT_TRUE : VARIANT_FALSE;
           break;
         }
         case eTextOrientation: {
-          Selection& currentSelection = CurrentSelection();
+          Selection& currentSelection = SelectionForTSFRef();
           paAttrVals[count].varValue.vt = VT_I4;
           paAttrVals[count].varValue.lVal =
             currentSelection.GetWritingMode().IsVertical() ? 2700 : 0;
           break;
         }
         default:
           MOZ_CRASH("Invalid index? Or not implemented yet?");
           break;
@@ -3561,17 +3561,17 @@ TSFTextStore::GetTextExt(TsViewCookie vc
 
   // NOTE: TSF (at least on Win 8.1) doesn't return TS_E_NOLAYOUT to the
   // caller even if we return it.  It's converted to just E_FAIL.
   // However, this is fixed on Win 10.
 
   const TSFStaticSink* kSink = TSFStaticSink::GetInstance();
   if (mComposition.IsComposing() && mComposition.mStart < acpEnd &&
       mContentForTSF.IsLayoutChangedAfter(acpEnd)) {
-    const Selection& currentSel = CurrentSelection();
+    const Selection& currentSel = SelectionForTSFRef();
     // The bug of Microsoft Office IME 2010 for Japanese is similar to
     // MS-IME for Win 8.1 and Win 10.  Newer version of MS Office IME is not
     // released yet.  So, we can hack it without prefs  because there must be
     // no developers who want to disable this hack for tests.
     const bool kIsMSOfficeJapaneseIME2010 =
       kSink->IsMSOfficeJapaneseIME2010Active();
     // MS IME for Japanese doesn't support asynchronous handling at deciding
     // its suggest list window position.  The feature was implemented
@@ -3914,21 +3914,21 @@ TSFTextStore::InsertTextAtSelection(DWOR
     if (!pacpStart || !pacpEnd) {
       MOZ_LOG(sTextStoreLog, LogLevel::Error,
              ("TSF: 0x%p   TSFTextStore::InsertTextAtSelection() FAILED due to "
               "null argument", this));
       return E_INVALIDARG;
     }
 
     // Get selection first
-    Selection& currentSel = CurrentSelection();
+    Selection& currentSel = SelectionForTSFRef();
     if (currentSel.IsDirty()) {
       MOZ_LOG(sTextStoreLog, LogLevel::Error,
              ("TSF: 0x%p   TSFTextStore::InsertTextAtSelection() FAILED due to "
-              "CurrentSelection() failure", this));
+              "SelectionForTSFRef() failure", this));
       return E_FAIL;
     }
 
     // Simulate text insertion
     *pacpStart = currentSel.StartOffset();
     *pacpEnd = currentSel.EndOffset();
     if (pChange) {
       pChange->acpStart = currentSel.StartOffset();
@@ -4134,21 +4134,21 @@ TSFTextStore::RecordCompositionStartActi
     return S_OK;
   }
 
   PendingAction* action = mPendingActions.AppendElement();
   action->mType = PendingAction::COMPOSITION_START;
   action->mSelectionStart = aStart;
   action->mSelectionLength = aLength;
 
-  Selection& currentSel = CurrentSelection();
+  Selection& currentSel = SelectionForTSFRef();
   if (currentSel.IsDirty()) {
     MOZ_LOG(sTextStoreLog, LogLevel::Error,
            ("TSF: 0x%p   TSFTextStore::RecordCompositionStartAction() FAILED "
-            "due to CurrentSelection() failure", this));
+            "due to SelectionForTSFRef() failure", this));
     action->mAdjustSelection = true;
   } else if (currentSel.MinOffset() != aStart ||
              currentSel.MaxOffset() != aStart + aLength) {
     // If new composition range is different from current selection range,
     // we need to set selection before dispatching compositionstart event.
     action->mAdjustSelection = true;
   } else {
     // We shouldn't dispatch selection set event before dispatching
@@ -4326,27 +4326,27 @@ TSFTextStore::OnUpdateComposition(ITfCom
   if (FAILED(hr)) {
     MOZ_LOG(sTextStoreLog, LogLevel::Error,
            ("TSF: 0x%p   TSFTextStore::OnUpdateComposition() FAILED due to "
             "RecordCompositionUpdateAction() failure", this));
     return hr;
   }
 
   if (MOZ_LOG_TEST(sTextStoreLog, LogLevel::Info)) {
-    Selection& currentSel = CurrentSelection();
+    Selection& currentSel = SelectionForTSFRef();
     if (currentSel.IsDirty()) {
       MOZ_LOG(sTextStoreLog, LogLevel::Error,
              ("TSF: 0x%p   TSFTextStore::OnUpdateComposition() FAILED due to "
-              "CurrentSelection() failure", this));
+              "SelectionForTSFRef() failure", this));
       return E_FAIL;
     }
     MOZ_LOG(sTextStoreLog, LogLevel::Info,
            ("TSF: 0x%p   TSFTextStore::OnUpdateComposition() succeeded: "
             "mComposition={ mStart=%ld, mString=\"%s\" }, "
-            "CurrentSelection()={ acpStart=%ld, acpEnd=%ld, style.ase=%s }",
+            "SelectionForTSFRef()={ acpStart=%ld, acpEnd=%ld, style.ase=%s }",
             this, mComposition.mStart,
             NS_ConvertUTF16toUTF8(mComposition.mString).get(),
             currentSel.StartOffset(), currentSel.EndOffset(),
             GetActiveSelEndName(currentSel.ActiveSelEnd())));
   }
   return S_OK;
 }
 
@@ -5112,21 +5112,21 @@ TSFTextStore::CreateNativeCaret()
     return;
   }
 
   MOZ_LOG(sTextStoreLog, LogLevel::Debug,
          ("TSF: 0x%p   TSFTextStore::CreateNativeCaret(), "
           "mComposition.IsComposing()=%s",
           this, GetBoolName(mComposition.IsComposing())));
 
-  Selection& currentSel = CurrentSelection();
+  Selection& currentSel = SelectionForTSFRef();
   if (currentSel.IsDirty()) {
     MOZ_LOG(sTextStoreLog, LogLevel::Error,
            ("TSF: 0x%p   TSFTextStore::CreateNativeCaret() FAILED due to "
-            "CurrentSelection() failure", this));
+            "SelectionForTSFRef() failure", this));
     return;
   }
 
   WidgetQueryContentEvent queryCaretRect(true, eQueryCaretRect, mWidget);
   mWidget->InitEvent(queryCaretRect);
 
   WidgetQueryContentEvent::Options options;
   // XXX If this is called without composition and the selection isn't

--- a/widget/windows/TSFTextStore.h
+++ b/widget/windows/TSFTextStore.h
@@ -565,27 +565,29 @@ protected:
     }
 
   private:
     TS_SELECTION_ACP mACP;
     WritingMode mWritingMode;
     bool mDirty;
   };
   // Don't access mSelection directly except at calling MarkDirty().
-  // Use CurrentSelection() instead.  This is modified immediately when
+  // Use SelectionForTSFRef() instead.  This is modified immediately when
   // TSF requests to set selection and not updated by selection change in
   // content until mContentForTSF is cleared.
   Selection mSelectionForTSF;
 
-  // Get "current selection".  If the document is locked, this initializes
-  // mSelection with the selection at the first call during a lock and returns
-  // it.  However, mSelection is NOT modified immediately.  When pending
-  // changes are flushed at unlocking the document, cached mSelection is
-  // modified.  Note that this is also called by ContentForTSFRef().
-  Selection& CurrentSelection();
+  /**
+   * Get the selection expected by TSF.  If mSelectionForTSF is already valid,
+   * this just return the reference to it.  Otherwise, this initializes it
+   * with eQuerySelectedText.  Please check if the result is valid before
+   * actually using it.
+   * Note that this is also called by ContentForTSFRef().
+   */
+  Selection& SelectionForTSFRef();
 
   struct PendingAction final
   {
     enum ActionType : uint8_t
     {
       COMPOSITION_START,
       COMPOSITION_UPDATE,
       COMPOSITION_END,