diff --git a/widget/windows/WinIMEHandler.cpp b/widget/windows/WinIMEHandler.cpp
index 7ca312ec808b..d65d5560d270 100644
--- a/widget/windows/WinIMEHandler.cpp
+++ b/widget/windows/WinIMEHandler.cpp
@@ -96,6 +96,42 @@ IMEHandler::IsComposingOn(nsWindow* aWindow)
   return nsIMM32Handler::IsComposingOn(aWindow);
 }
 
+// static
+nsresult
+IMEHandler::NotifyIME(nsWindow* aWindow,
+                      NotificationToIME aNotification)
+{
+#ifdef NS_ENABLE_TSF
+  if (sIsInTSFMode) {
+    switch (aNotification) {
+      case REQUEST_TO_COMMIT_COMPOSITION:
+        if (nsTextStore::IsComposingOn(aWindow)) {
+          nsTextStore::CommitComposition(false);
+        }
+        return NS_OK;
+      case REQUEST_TO_CANCEL_COMPOSITION:
+        if (nsTextStore::IsComposingOn(aWindow)) {
+          nsTextStore::CommitComposition(true);
+        }
+        return NS_OK;
+      default:
+        return NS_ERROR_NOT_IMPLEMENTED;
+    }
+  }
+#endif //NS_ENABLE_TSF
+
+  switch (aNotification) {
+    case REQUEST_TO_COMMIT_COMPOSITION:
+      nsIMM32Handler::CommitComposition(aWindow);
+      return NS_OK;
+    case REQUEST_TO_CANCEL_COMPOSITION:
+      nsIMM32Handler::CancelComposition(aWindow);
+      return NS_OK;
+    default:
+      return NS_ERROR_NOT_IMPLEMENTED;
+  }
+}
+
 #ifdef DEBUG
 // static
 bool
diff --git a/widget/windows/WinIMEHandler.h b/widget/windows/WinIMEHandler.h
index 63920320be56..0a69208b009d 100644
--- a/widget/windows/WinIMEHandler.h
+++ b/widget/windows/WinIMEHandler.h
@@ -7,6 +7,7 @@
 #define WinIMEHandler_h_
 
 #include "nscore.h"
+#include "nsEvent.h"
 #include <windows.h>
 
 class nsWindow;
@@ -47,6 +48,12 @@ public:
    */
   static bool IsComposingOn(nsWindow* aWindow);
 
+  /**
+   * Notifies IME of the notification (a request or an event).
+   */
+  static nsresult NotifyIME(nsWindow* aWindow,
+                            NotificationToIME aNotification);
+
   /**
    * "Kakutei-Undo" of ATOK or WXG (both of them are Japanese IME) causes
    * strange WM_KEYDOWN/WM_KEYUP/WM_CHAR message pattern.  So, when this
diff --git a/widget/windows/nsTextStore.h b/widget/windows/nsTextStore.h
index 9fa14fff167f..b52bf877a901 100644
--- a/widget/windows/nsTextStore.h
+++ b/widget/windows/nsTextStore.h
@@ -101,7 +101,7 @@ public:
 
   static void     CommitComposition(bool aDiscard)
   {
-    if (!sTsfTextStore) return;
+    NS_ENSURE_TRUE_VOID(sTsfTextStore);
     sTsfTextStore->CommitCompositionInternal(aDiscard);
   }
 
diff --git a/widget/windows/nsWindow.cpp b/widget/windows/nsWindow.cpp
index 33f01e7ef6ba..2412295b072f 100644
--- a/widget/windows/nsWindow.cpp
+++ b/widget/windows/nsWindow.cpp
@@ -7384,16 +7384,7 @@ nsWindow::OnSysColorChanged()
 
 NS_IMETHODIMP nsWindow::ResetInputState()
 {
-#ifdef DEBUG_KBSTATE
-  PR_LOG(gWindowsLog, PR_LOG_ALWAYS, ("ResetInputState\n"));
-#endif
-
-#ifdef NS_ENABLE_TSF
-  nsTextStore::CommitComposition(false);
-#endif //NS_ENABLE_TSF
-
-  nsIMM32Handler::CommitComposition(this);
-  return NS_OK;
+  return IMEHandler::NotifyIME(this, REQUEST_TO_COMMIT_COMPOSITION);
 }
 
 NS_IMETHODIMP_(void)
@@ -7462,16 +7453,7 @@ nsWindow::GetInputContext()
 
 NS_IMETHODIMP nsWindow::CancelIMEComposition()
 {
-#ifdef DEBUG_KBSTATE
-  PR_LOG(gWindowsLog, PR_LOG_ALWAYS, ("CancelIMEComposition\n"));
-#endif 
-
-#ifdef NS_ENABLE_TSF
-  nsTextStore::CommitComposition(true);
-#endif //NS_ENABLE_TSF
-
-  nsIMM32Handler::CancelComposition(this);
-  return NS_OK;
+  return IMEHandler::NotifyIME(this, REQUEST_TO_CANCEL_COMPOSITION);
 }
 
 NS_IMETHODIMP