Merge mozilla-central to autoland. a=merge

browser/base/content/tabbrowser-tabs.js

@@ -1474,10 +1474,7 @@
           );
           tab._pinnedUnscrollable = true;
         }
-        this.style.setProperty(
-          "--tab-overflow-pinned-tabs-width",
-          width + "px"
-        );
+        this.style.paddingInlineStart = width + "px";
       } else {
         this.removeAttribute("positionpinnedtabs");
 
@@ -1487,7 +1484,7 @@
           tab._pinnedUnscrollable = false;
         }
 
-        this.style.removeProperty("--tab-overflow-pinned-tabs-width");
+        this.style.paddingInlineStart = "";
       }
 
       if (this._lastNumPinned != numPinned) {

browser/themes/shared/tabs.css

@@ -48,8 +48,6 @@
 #tabbrowser-tabs {
   --tab-min-width: 76px;
   --tab-loading-fill: #0A84FF;
-  --tab-overflow-pinned-tabs-width: 0px;
-  padding-inline-start: var(--tab-overflow-pinned-tabs-width);
 }
 
 #tabbrowser-tabpanels {
@@ -684,7 +682,7 @@
 
 :is(#firefox-view-button, #wrapper-firefox-view-button) + #tabbrowser-tabs {
   border-inline-start: 1px solid color-mix(in srgb, currentColor 25%, transparent);
-  padding-inline-start: calc(var(--tab-overflow-pinned-tabs-width) + 4px);
+  padding-inline-start: 4px;
   margin-inline-start: 4px;
 }