feat: Remove legacy pref checking for gradient themes, b=bug #11375, c=common, workspaces

prefs/zen/theme.yaml

@@ -11,9 +11,6 @@
 - name: zen.theme.dark-mode-bias
   value: 0.3
 
-- name: zen.theme.gradient
-  value: true
-
 - name: zen.theme.gradient.show-custom-colors
   value: false
 

src/zen/common/styles/zen-browser-ui.css

@@ -54,29 +54,27 @@
     pointer-events: none;
   }
 
-  @media -moz-pref('zen.theme.gradient') {
+  &::after {
+    background: var(--zen-main-browser-background);
+    opacity: var(--zen-background-opacity);
+    transition: 0s;
+  }
+
+  &:is(.zen-toolbar-background) {
     &::after {
-      background: var(--zen-main-browser-background);
-      opacity: var(--zen-background-opacity);
-      transition: 0s;
+      background: var(--zen-main-browser-background-toolbar);
     }
+  }
 
-    &:is(.zen-toolbar-background) {
-      &::after {
-        background: var(--zen-main-browser-background-toolbar);
-      }
-    }
+  &::before {
+    background: var(--zen-main-browser-background-old);
+    opacity: calc(1 - var(--zen-background-opacity));
+    transition: 0s;
+  }
 
+  &:is(.zen-toolbar-background) {
     &::before {
-      background: var(--zen-main-browser-background-old);
-      opacity: calc(1 - var(--zen-background-opacity));
-      transition: 0s;
-    }
-
-    &:is(.zen-toolbar-background) {
-      &::before {
-        background: var(--zen-main-browser-background-toolbar-old);
-      }
+      background: var(--zen-main-browser-background-toolbar-old);
     }
   }
 

src/zen/workspaces/ZenGradientGenerator.mjs

@@ -66,11 +66,7 @@ export class nsZenThemePicker extends nsZenMultiWindowFeature {
 
   constructor() {
     super();
-    if (
-      !Services.prefs.getBoolPref('zen.theme.gradient', true) ||
-      !gZenWorkspaces.shouldHaveWorkspaces ||
-      gZenWorkspaces.privateWindowOrDisabled
-    ) {
+    if (!gZenWorkspaces.shouldHaveWorkspaces || gZenWorkspaces.privateWindowOrDisabled) {
       return;
     }
     this.promiseInitialized = new Promise((resolve) => {