diff --git a/layout/forms/nsFormControlFrame.cpp b/layout/forms/nsFormControlFrame.cpp
index 3c2aa0d5d6dd..0add45ae6497 100644
--- a/layout/forms/nsFormControlFrame.cpp
+++ b/layout/forms/nsFormControlFrame.cpp
@@ -607,6 +607,9 @@ NS_METHOD nsFormControlFrame::HandleEvent(nsIPresContext& aPresContext,
       case NS_MOUSE_EXIT:
         mLastMouseState = eMouseNone;
         break;
+      case NS_CONTROL_CHANGE:
+        ControlChanged(&aPresContext);
+        break;
     }
   }
 
diff --git a/layout/forms/nsFormControlFrame.h b/layout/forms/nsFormControlFrame.h
index b16067c6e10c..dd21114c59e8 100644
--- a/layout/forms/nsFormControlFrame.h
+++ b/layout/forms/nsFormControlFrame.h
@@ -133,6 +133,11 @@ public:
     */
   virtual void MouseClicked(nsIPresContext* aPresContext) {}
 
+  /**
+    * Respond to a control change (e.g. combo box close-up)
+    */
+  virtual void ControlChanged(nsIPresContext* aPresContext) {}
+
   /**
     * Perform opertations after the widget associated with this frame has been
     * created.
diff --git a/layout/html/forms/src/nsFormControlFrame.cpp b/layout/html/forms/src/nsFormControlFrame.cpp
index 3c2aa0d5d6dd..0add45ae6497 100644
--- a/layout/html/forms/src/nsFormControlFrame.cpp
+++ b/layout/html/forms/src/nsFormControlFrame.cpp
@@ -607,6 +607,9 @@ NS_METHOD nsFormControlFrame::HandleEvent(nsIPresContext& aPresContext,
       case NS_MOUSE_EXIT:
         mLastMouseState = eMouseNone;
         break;
+      case NS_CONTROL_CHANGE:
+        ControlChanged(&aPresContext);
+        break;
     }
   }
 
diff --git a/layout/html/forms/src/nsFormControlFrame.h b/layout/html/forms/src/nsFormControlFrame.h
index b16067c6e10c..dd21114c59e8 100644
--- a/layout/html/forms/src/nsFormControlFrame.h
+++ b/layout/html/forms/src/nsFormControlFrame.h
@@ -133,6 +133,11 @@ public:
     */
   virtual void MouseClicked(nsIPresContext* aPresContext) {}
 
+  /**
+    * Respond to a control change (e.g. combo box close-up)
+    */
+  virtual void ControlChanged(nsIPresContext* aPresContext) {}
+
   /**
     * Perform opertations after the widget associated with this frame has been
     * created.