--- a/browser/themes/shared/notification-icons.inc.css
+++ b/browser/themes/shared/notification-icons.inc.css
@@ -34,28 +34,16 @@
 %ifdef MOZ_WIDGET_GTK
     list-style-image: url(moz-icon://stock/gtk-dialog-info?size=dialog);
 %else
     list-style-image: url(chrome://global/skin/icons/information-32.png);
 %endif
   }
 }
 
-#notification-popup > .panel-arrowcontainer > .panel-arrowcontent {
-  /* In order to display the action buttons near the edge of the arrow panel we
-   * have to reset its default padding and specify the padding in the individual
-   * "popupnotification" elements instead. To keep the rounded borders of the
-   * panel, we also have to ensure the contents are clipped to the border box
-   * by hiding the overflow, and we have to override the "display" property so
-   * that the height of the contents is computed correctly in that case. */
-  padding: 0;
-  overflow: hidden;
-  display: block;
-}
-
 .notification-anchor-icon:not(.plugin-blocked):-moz-lwtheme,
 #blocked-permissions-container > .blocked-permission-icon:-moz-lwtheme {
   filter: url(chrome://global/skin/filters.svg#fill);
   fill: currentColor;
 }
 
 .notification-anchor-icon:not(.plugin-blocked):not(:hover) {
   opacity: .8;

--- a/toolkit/themes/linux/global/jar.mn
+++ b/toolkit/themes/linux/global/jar.mn
@@ -17,17 +17,17 @@ toolkit.jar:
    skin/classic/global/global.css
    skin/classic/global/groupbox.css
    skin/classic/global/listbox.css
    skin/classic/global/menu.css
    skin/classic/global/menulist.css
    skin/classic/global/netError.css
 *  skin/classic/global/notification.css
    skin/classic/global/numberbox.css
-   skin/classic/global/popup.css
+*  skin/classic/global/popup.css
    skin/classic/global/preferences.css
    skin/classic/global/printPageSetup.css
    skin/classic/global/printPreview.css
    skin/classic/global/radio.css
    skin/classic/global/scrollbox.css
    skin/classic/global/splitter.css
    skin/classic/global/tabbox.css
    skin/classic/global/textbox.css

--- a/toolkit/themes/linux/global/popup.css
+++ b/toolkit/themes/linux/global/popup.css
@@ -35,16 +35,18 @@ panel[type="arrow"][side="right"] {
   padding: var(--arrowpanel-padding);
   color: var(--arrowpanel-color);
   background: var(--arrowpanel-background);
   border: 1px solid var(--arrowpanel-border-color);
   box-shadow: 0 0 4px hsla(0,0%,0%,.2);
   margin: 4px;
 }
 
+%include ../../shared/notification-popup.inc.css
+
 .panel-arrow[side="top"],
 .panel-arrow[side="bottom"] {
   list-style-image: var(--panel-arrow-image-vertical,
                         url("chrome://global/skin/arrow/panelarrow-vertical-themed.svg"));
   position: relative;
   margin-left: 10px;
   margin-right: 10px;
 }

--- a/toolkit/themes/osx/global/jar.mn
+++ b/toolkit/themes/osx/global/jar.mn
@@ -22,17 +22,17 @@ toolkit.jar:
   skin/classic/global/groupbox.css
   skin/classic/global/linkTree.css
   skin/classic/global/listbox.css
   skin/classic/global/menu.css
   skin/classic/global/menulist.css
 * skin/classic/global/notification.css
   skin/classic/global/netError.css
   skin/classic/global/numberbox.css
-  skin/classic/global/popup.css
+* skin/classic/global/popup.css
   skin/classic/global/preferences.css
   skin/classic/global/progressmeter.css
   skin/classic/global/radio.css
   skin/classic/global/resizer.css
   skin/classic/global/richlistbox.css
   skin/classic/global/scrollbars.css                                 (nativescrollbars.css)
   skin/classic/global/scale.css
   skin/classic/global/scrollbox.css

--- a/toolkit/themes/osx/global/popup.css
+++ b/toolkit/themes/osx/global/popup.css
@@ -45,16 +45,18 @@ panel[type="arrow"][side="right"] {
   border-radius: var(--arrowpanel-border-radius);
   box-shadow: 0 0 0 1px var(--arrowpanel-border-color);
   color: var(--arrowpanel-color);
   border: none;
   padding: var(--arrowpanel-padding);
   margin: 1px;
 }
 
+%include ../../shared/notification-popup.inc.css
+
 .panel-arrow[side="top"] {
   list-style-image: var(--panel-arrow-image-vertical,
                         url("chrome://global/skin/arrow/panelarrow-vertical.png"));
   margin-left: 16px;
   margin-right: 16px;
   margin-bottom: -1px;
 }
 

new file mode 100644
--- /dev/null
+++ b/toolkit/themes/shared/notification-popup.inc.css
@@ -0,0 +1,11 @@
+#notification-popup > .panel-arrowcontainer > .panel-arrowcontent {
+  /* In order to display the action buttons near the edge of the arrow panel we
+   * have to reset its default padding and specify the padding in the individual
+   * "popupnotification" elements instead. To keep the rounded borders of the
+   * panel, we also have to ensure the contents are clipped to the border box
+   * by hiding the overflow, and we have to override the "display" property so
+   * that the height of the contents is computed correctly in that case. */
+  padding: 0;
+  overflow: hidden;
+  display: block;
+}

--- a/toolkit/themes/windows/global/popup.css
+++ b/toolkit/themes/windows/global/popup.css
@@ -52,16 +52,18 @@ panel[type="arrow"][side="right"] {
   color: var(--arrowpanel-color);
   background: var(--arrowpanel-background);
   background-clip: padding-box;
   border: 1px solid var(--arrowpanel-border-color);
   box-shadow: 0 0 4px hsla(0,0%,0%,.2);
   margin: 4px;
 }
 
+%include ../../shared/notification-popup.inc.css
+
 %ifdef XP_WIN
 @media (-moz-os-version: windows-xp),
        (-moz-os-version: windows-vista),
        (-moz-os-version: windows-win7) {
 %endif
 .panel-arrowcontent {
   border-radius: 4px;
 }