diff --git a/layout/forms/nsListControlFrame.cpp b/layout/forms/nsListControlFrame.cpp
index 6f9cf59da243..9f84dbf15037 100644
--- a/layout/forms/nsListControlFrame.cpp
+++ b/layout/forms/nsListControlFrame.cpp
@@ -2778,6 +2778,7 @@ nsListControlFrame::MouseUp(nsIDOMEvent* aMouseEvent)
 
   // only allow selection with the left button
   if (!IsLeftButton(aMouseEvent)) {
+    // IsLeftButton Prevents all propragation of the event
     return NS_ERROR_FAILURE; // means consume event
   }
 
@@ -2823,13 +2824,6 @@ nsListControlFrame::MouseUp(nsIDOMEvent* aMouseEvent)
 #endif
   }
 
-  if (IsInDropDownMode() == PR_TRUE) {
-    aMouseEvent->PreventDefault();
-    aMouseEvent->PreventCapture();
-    aMouseEvent->PreventBubble();
-    REFLOW_DEBUG_MSG(">>>>>> Returning and preventing bubbling");
-    return NS_ERROR_FAILURE; //consumes event
-  }
   return NS_OK;
 }
 
@@ -2924,9 +2918,7 @@ nsListControlFrame::MouseDown(nsIDOMEvent* aMouseEvent)
 
   // only allow selection with the left button
   if (!IsLeftButton(aMouseEvent)) {
-    aMouseEvent->PreventDefault();
-    aMouseEvent->PreventCapture();
-    aMouseEvent->PreventBubble();
+    // IsLeftButton Prevents all propragation of the event
     return NS_ERROR_FAILURE; // means consume event
   }
 
@@ -3022,12 +3014,6 @@ nsListControlFrame::MouseDown(nsIDOMEvent* aMouseEvent)
     }
   }
 
-  if (IsInDropDownMode() == PR_TRUE) {
-    aMouseEvent->PreventDefault();
-    aMouseEvent->PreventCapture();
-    aMouseEvent->PreventBubble();
-    return NS_ERROR_FAILURE; //consumes event
-  }
   return NS_OK;
 }
 
diff --git a/layout/html/forms/src/nsGfxListControlFrame.cpp b/layout/html/forms/src/nsGfxListControlFrame.cpp
index b18ce43d80af..19cd902d0432 100644
--- a/layout/html/forms/src/nsGfxListControlFrame.cpp
+++ b/layout/html/forms/src/nsGfxListControlFrame.cpp
@@ -2939,6 +2939,7 @@ nsGfxListControlFrame::MouseUp(nsIDOMEvent* aMouseEvent)
 
   // only allow selection with the left button
   if (!IsLeftButton(aMouseEvent)) {
+    // IsLeftButton Prevents all propragation of the event
     return NS_ERROR_FAILURE; // means consume event
   }
 
@@ -2978,12 +2979,6 @@ nsGfxListControlFrame::MouseUp(nsIDOMEvent* aMouseEvent)
     }
   }
 
-  if (IsInDropDownMode() == PR_TRUE) {
-    aMouseEvent->PreventDefault();
-    aMouseEvent->PreventCapture();
-    aMouseEvent->PreventBubble();
-    return NS_ERROR_FAILURE; //consumes event
-  }
   return NS_OK;
 }
 
@@ -3084,6 +3079,7 @@ nsGfxListControlFrame::MouseDown(nsIDOMEvent* aMouseEvent)
 
   // only allow selection with the left button
   if (!IsLeftButton(aMouseEvent)) {
+    // IsLeftButton Prevents all propragation of the event
     return NS_ERROR_FAILURE; // means consume event
   }
 
@@ -3197,12 +3193,6 @@ nsGfxListControlFrame::MouseDown(nsIDOMEvent* aMouseEvent)
     }
   }
 
-  if (IsInDropDownMode() == PR_TRUE) {
-    aMouseEvent->PreventDefault();
-    aMouseEvent->PreventCapture();
-    aMouseEvent->PreventBubble();
-    return NS_ERROR_FAILURE; //consumes event
-  }
   return NS_OK;
 }
 
diff --git a/layout/html/forms/src/nsListControlFrame.cpp b/layout/html/forms/src/nsListControlFrame.cpp
index 6f9cf59da243..9f84dbf15037 100644
--- a/layout/html/forms/src/nsListControlFrame.cpp
+++ b/layout/html/forms/src/nsListControlFrame.cpp
@@ -2778,6 +2778,7 @@ nsListControlFrame::MouseUp(nsIDOMEvent* aMouseEvent)
 
   // only allow selection with the left button
   if (!IsLeftButton(aMouseEvent)) {
+    // IsLeftButton Prevents all propragation of the event
     return NS_ERROR_FAILURE; // means consume event
   }
 
@@ -2823,13 +2824,6 @@ nsListControlFrame::MouseUp(nsIDOMEvent* aMouseEvent)
 #endif
   }
 
-  if (IsInDropDownMode() == PR_TRUE) {
-    aMouseEvent->PreventDefault();
-    aMouseEvent->PreventCapture();
-    aMouseEvent->PreventBubble();
-    REFLOW_DEBUG_MSG(">>>>>> Returning and preventing bubbling");
-    return NS_ERROR_FAILURE; //consumes event
-  }
   return NS_OK;
 }
 
@@ -2924,9 +2918,7 @@ nsListControlFrame::MouseDown(nsIDOMEvent* aMouseEvent)
 
   // only allow selection with the left button
   if (!IsLeftButton(aMouseEvent)) {
-    aMouseEvent->PreventDefault();
-    aMouseEvent->PreventCapture();
-    aMouseEvent->PreventBubble();
+    // IsLeftButton Prevents all propragation of the event
     return NS_ERROR_FAILURE; // means consume event
   }
 
@@ -3022,12 +3014,6 @@ nsListControlFrame::MouseDown(nsIDOMEvent* aMouseEvent)
     }
   }
 
-  if (IsInDropDownMode() == PR_TRUE) {
-    aMouseEvent->PreventDefault();
-    aMouseEvent->PreventCapture();
-    aMouseEvent->PreventBubble();
-    return NS_ERROR_FAILURE; //consumes event
-  }
   return NS_OK;
 }