Tweak some scrollbox styling to fix fallout from bug 1913322

chrome/hide_tabs_scrollbuttons.css

@@ -55,7 +55,9 @@ spacer[part="overflow-end-indicator"]{
   margin-inline-end: calc(0px - var(--tab-shadow-max-size,0px)) !important;
   background-image: var(--uc-scrollbutton-down-background);
 }
+scrollbox[orient="horizontal"],
 .scrollbox-clip{ margin-inline: var(--uc-scrollbox-margin,0px); }
+.scrollbox-clip > scrollbox[orient="horizontal"]{ margin-inline: initial }
 
 /* Need to reset some things for other scrollboxes */
 .menupopup-arrowscrollbox{

chrome/multi-row_tabs.css

@@ -26,6 +26,7 @@ See the above repository for updates as well as full license text. */
   #scrollbutton-up,
   #scrollbutton-down{ display: var(--scrollbutton-display-model,initial) }
 
+  scrollbox[part][orient="horizontal"] > slot,
   scrollbox[part][orient="horizontal"]{
     display: flex;
     flex-wrap: wrap;
@@ -36,6 +37,9 @@ See the above repository for updates as well as full license text. */
     scrollbar-gutter: stable;
     scroll-snap-type: y mandatory;
   }
+  scrollbox[part][orient="horizontal"] > slot{
+    overflow-x: hidden;
+  }
 }
 
 .scrollbox-clip[orient="horizontal"],

chrome/multi-row_tabs_below_content.css

@@ -161,6 +161,7 @@ See the above repository for updates as well as full license text. */
   #scrollbutton-up,
   #scrollbutton-down{ display: var(--scrollbutton-display-model,initial) }
 
+  scrollbox[part][orient="horizontal"] > slot,
   scrollbox[part][orient="horizontal"]{
     display: flex;
     flex-wrap: wrap;
@@ -171,7 +172,9 @@ See the above repository for updates as well as full license text. */
     scrollbar-gutter: stable;
     scroll-snap-type: y mandatory;
   }
-
+  scrollbox[part][orient="horizontal"] > slot{
+    overflow-x: hidden;
+  }
   .scrollbox-clip[orient="horizontal"],
   #tabbrowser-arrowscrollbox{
     overflow: -moz-hidden-unscrollable;

chrome/multi-row_tabs_separate_pinned_row_patch.css

@@ -3,7 +3,8 @@ See the above repository for updates as well as full license text. */
 
 /* Use with multi-row_tabs.css to show pinned tabs on separate row. */
 
-scrollbox[part][orient="horizontal"]::after{
+scrollbox[part][orient="horizontal"] > slot::after,
+.scrollbox-clip > scrollbox[part][orient="horizontal"]::after{
   display: flow-root list-item;
   content: "";
   flex-basis: -moz-available;
@@ -16,6 +17,6 @@ scrollbox[part][orient="horizontal"]::after{
   order: 1;
 }
 
-.tabbrowser-tab[first-visible-unpinned-tab]{
+.tabbrowser-tab[pinned] + .tabbrowser-tab{
   margin-inline-start: 0 !important;
 }

chrome/tabs_animated_gradient_border.css

@@ -39,6 +39,7 @@ Thanks to /u/skenera on reddit for suggesting animating background position and
   margin-inline: 0 !important;
   --tab-shadow-max-size: 0px;
 }
+scrollbox[orient="horizontal"] > slot::after,
 .scrollbox-clip[orient="horizontal"] > scrollbox::after{
   content: "";
   display: flex;

chrome/toolbarbuttons_in_tabs_periphery.css

@@ -38,8 +38,11 @@ Any button to the right of the flexible space is pushed to the right edge.
 .closing-tabs-spacer{
   display: none !important;
 }
-.scrollbox-clip[orient="horizontal"]{
-  contain: var(--uc-scrollbox-containment,initial) !important;
+@-moz-document url("chrome://browser/content/browser.xhtml"){
+  scrollbox[orient="horizontal"],
+  .scrollbox-clip[orient="horizontal"]{
+    contain: var(--uc-scrollbox-containment,initial) !important;
+  }
 }
 #tabbrowser-tabs ~ toolbarspring{
   flex-grow: 0 !important;

chrome/vertical_context_navigation.css

@@ -7,6 +7,7 @@ See the above repository for updates as well as full license text. */
 #contentAreaContextMenu{
   --uc-popup-display: grid;
   --uc-pseudo-elem: "";
+  --uc-scrollbox-slot: contents;
   min-height: 162px;
 }
 scrollbox[orient="vertical"]{
@@ -14,7 +15,9 @@ scrollbox[orient="vertical"]{
   grid-template-columns: auto 1fr; 
   grid-template-rows: 0;
 }
-
+scrollbox[orient="vertical"] > slot{
+  display: var(--uc-scrollbox-slot,initial) !important;
+}
 scrollbox[orient="vertical"]::before{
   content: var(--uc-pseudo-elem,none);
   grid-area: auto / 2 / auto / 2;