Bug 1720880 - Consolidate a bit bookmarks popup styles. r=dao

Unify shared declarations, and avoid unneeded [placespopup=true], since
there's no element that matches:

  :is(#BMB_bookmarksPopup, #PlacesToolbar) menupopup:not([placespopup])

Depends on D120080

Differential Revision: https://phabricator.services.mozilla.com/D120197

browser/themes/linux/customizableui/panelUI.css

@@ -27,9 +27,6 @@
 }
 
 #BMB_bookmarksPopup menupopup {
-  --panel-background: var(--arrowpanel-background);
-  --panel-color: var(--arrowpanel-color);
-  --panel-border-color: var(--arrowpanel-border-color);
   margin-top: -9px; /* The top component of --panel-subview-body-padding and the 1px border */
  }
 
@@ -39,7 +36,7 @@
   margin-top: -4px;
 }
 
-#PlacesToolbar menupopup[placespopup=true]::part(content) {
+#PlacesToolbar menupopup::part(content) {
   box-shadow: 0 0 4px hsla(0, 0%, 0%, 0.2);
   background: var(--arrowpanel-background);
   border: 1px solid var(--arrowpanel-border-color);

browser/themes/osx/customizableui/panelUI.css

@@ -65,14 +65,6 @@ panelmultiview .toolbaritem-combined-buttons > spacer.before-label {
   display: none;
 }
 
-#BMB_bookmarksPopup menupopup[placespopup=true] {
-  appearance: none;
-  background: transparent;
-  --panel-background: var(--arrowpanel-background);
-  --panel-border-color: var(--arrowpanel-border-color);
-  --panel-color: var(--arrowpanel-color);
-}
-
 /* Override OSX-specific toolkit styles for the bookmarks panel */
 menu.subviewbutton > .menu-right {
   margin-inline-end: -4px;

browser/themes/shared/customizableui/panelUI.inc.css

@@ -232,6 +232,11 @@ panelview .toolbaritem-combined-buttons,
 }
 
 #BMB_bookmarksPopup menupopup {
+  appearance: none;
+  background-color: transparent;
+  --panel-background: var(--arrowpanel-background);
+  --panel-color: var(--arrowpanel-color);
+  --panel-border-color: var(--arrowpanel-border-color);
   --panel-border-radius: var(--arrowpanel-border-radius);
   --panel-padding: var(--panel-subview-body-padding);
 }

browser/themes/windows/customizableui/panelUI.css

@@ -32,36 +32,31 @@
   margin-top: -2px;
 }
 
-#PlacesToolbar menupopup[placespopup=true],
-#BMB_bookmarksPopup menupopup[placespopup=true] {
+#PlacesToolbar menupopup,
+#BMB_bookmarksPopup menupopup {
   appearance: none;
   border: none;
   padding-inline-start: 3px;
 }
 
-#BMB_bookmarksPopup menupopup[placespopup=true] {
-  background-color: transparent;
+#BMB_bookmarksPopup menupopup {
   -moz-window-shadow: none;
-
-  --panel-background: var(--arrowpanel-background);
-  --panel-color: var(--arrowpanel-color);
-  --panel-border-color: var(--arrowpanel-border-color);
   margin-top: -13px; /* 8px of padding, 4px of shadow margin, 1px of border */
 }
 
-#PlacesToolbar menupopup[placespopup=true] {
+#PlacesToolbar menupopup {
   background: transparent;
   padding-top: 4px;
   margin-inline-start: -3px;
 }
 
-#BMB_bookmarksPopup menupopup[placespopup=true]::part(content) {
+#BMB_bookmarksPopup menupopup::part(content) {
   /* emulating MozPlacesPopupArrow but without the arrow */
   box-shadow: var(--windows-panel-box-shadow);
   margin: 4px;
 }
 
-#PlacesToolbar menupopup[placespopup=true]::part(content) {
+#PlacesToolbar menupopup::part(content) {
   box-shadow: 0 0 4px rgba(0,0,0,0.2);
   background: var(--arrowpanel-background);
   color: var(--arrowpanel-color);
@@ -72,7 +67,7 @@
 
 /* Add border-radius on Windows 7 */
 @media (-moz-os-version: windows-win7) {
-  #BMB_bookmarksPopup menupopup[placespopup=true]::part(content) {
+  #BMB_bookmarksPopup menupopup::part(content) {
     border-radius: 3.5px;
   }
 }