chore: Cleanup calls to updateSplitViewButton, b=(no-bug), c=split-view

Author: mr-cheffy

src/zen/split-view/ZenViewSplitter.mjs

@@ -993,7 +993,6 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
       tab = tab.parentNode.closest('.tabbrowser-tab');
       console.assert(tab, 'Tab not found for zen-glance-tab');
     }
-    this.updateSplitViewButton(!tab?.splitView);
     if (tab) {
       this.updateSplitView(tab);
       tab.linkedBrowser.docShellIsActive = true;
@@ -1127,7 +1126,6 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
 
     if (oldView === newView) return;
     if (newView < 0 && oldView >= 0) {
-      this.updateSplitViewButton(true);
       this.deactivateCurrentSplitView();
       return;
     }
@@ -1147,7 +1145,6 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
     }
     this.removeSplitters();
     this.tabBrowserPanel.removeAttribute('zen-split-view');
-    this.updateSplitViewButton(true);
     this.currentView = -1;
     this.toggleWrapperDisplay(false);
   }
@@ -1171,7 +1168,6 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
 
     this.tabBrowserPanel.setAttribute('zen-split-view', 'true');
 
-    this.updateSplitViewButton(false);
     this.applyGridToTabs(splitData.tabs);
     this.applyGridLayout(splitData.layoutTree);
     this.setTabsDocShellState(splitData.tabs, true);
@@ -1498,20 +1494,6 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
     container.style.inset = '';
   }
 
-  /**
-   * Updates the split view button visibility.
-   *
-   * @param {boolean} hidden - Indicates if the button should be hidden.
-   */
-  updateSplitViewButton(hidden) {
-    const button = document.getElementById('zen-split-views-box');
-    if (hidden) {
-      button?.setAttribute('hidden', 'true');
-    } else {
-      button?.removeAttribute('hidden');
-    }
-  }
-
   /**
    * Updates the UI of the panel.
    *

src/zen/split-view/zen-decks.css

@@ -112,10 +112,6 @@
   cursor: ns-resize;
 }
 
-#zen-split-views-box:not([hidden='true']) {
-  display: flex !important;
-}
-
 .zen-view-splitter-header-container {
   position: absolute;
   top: calc(var(--zen-split-column-gap) / -2);