[DevTools] Disable the tree list for now (facebook#34606)

When there are no named Activities we should hide the tree side panel
(and the button to show it). Since it's not implemented yet there are
never any ones so it's always hidden.

Author: sebmarkbage

packages/react-devtools-shared/src/devtools/views/SuspenseTab/SuspenseTab.js

@@ -117,6 +117,11 @@ function SuspenseTab(_: {}) {
     initLayoutState,
   );
 
+  // If there are no named Activity boundaries, we don't have any tree list and we should hide
+  // both the panel and the button to toggle it. Since we currently don't support it yet, it's
+  // always disabled.
+  const treeListDisabled = true;
+
   const wrapperTreeRef = useRef<null | HTMLElement>(null);
   const resizeTreeRef = useRef<null | HTMLElement>(null);
   const resizeTreeListRef = useRef<null | HTMLElement>(null);
@@ -290,23 +295,31 @@ function SuspenseTab(_: {}) {
   return (
     <div className={styles.SuspenseTab} ref={wrapperTreeRef}>
       <div className={styles.TreeWrapper} ref={resizeTreeRef}>
-        <div
-          className={styles.TreeList}
-          hidden={treeListHidden}
-          ref={resizeTreeListRef}>
-          <SuspenseTreeList />
-        </div>
-        <div className={styles.ResizeBarWrapper} hidden={treeListHidden}>
+        {treeListDisabled ? null : (
           <div
-            onPointerDown={onResizeStart}
-            onPointerMove={onResizeTreeList}
-            onPointerUp={onResizeEnd}
-            className={styles.ResizeBar}
-          />
-        </div>
+            className={styles.TreeList}
+            hidden={treeListHidden}
+            ref={resizeTreeListRef}>
+            <SuspenseTreeList />
+          </div>
+        )}
+        {treeListDisabled ? null : (
+          <div className={styles.ResizeBarWrapper} hidden={treeListHidden}>
+            <div
+              onPointerDown={onResizeStart}
+              onPointerMove={onResizeTreeList}
+              onPointerUp={onResizeEnd}
+              className={styles.ResizeBar}
+            />
+          </div>
+        )}
         <div className={styles.TreeView}>
           <div className={styles.SuspenseTreeViewHeader}>
-            <ToggleTreeList dispatch={dispatch} state={state} />
+            {treeListDisabled ? (
+              <div />
+            ) : (
+              <ToggleTreeList dispatch={dispatch} state={state} />
+            )}
             <div className={styles.SuspenseTreeViewHeaderMain}>
               <div className={styles.SuspenseTimeline}>
                 <SuspenseTimeline />