Revert "LibJS: Remove "uprooting" mechanism from garbage collector"

This reverts commit 6232ad3a0d.

Unfortunately this introduced some flakiness on CI, so it wasn't
quite this simple.

Userland/Libraries/LibJS/Tests/builtins/FinalizationRegistry/FinalizationRegistry.prototype.cleanupSome.js

@@ -3,7 +3,9 @@ test("length is 0", () => {
 });
 
 function registerInDifferentScope(registry) {
-    registry.register({}, {});
+    const target = {};
+    registry.register(target, {});
+    return target;
 }
 
 test("basic functionality", () => {
@@ -18,7 +20,8 @@ test("basic functionality", () => {
 
     expect(count).toBe(0);
 
-    registerInDifferentScope(registry);
+    const target = registerInDifferentScope(registry);
+    markAsGarbage("target");
     gc();
 
     registry.cleanupSome(increment);

Userland/Libraries/LibJS/Tests/builtins/WeakMap/WeakMap.prototype.set.js

@@ -1,9 +1,3 @@
-function registerInDifferentScope(registry) {
-    const target = {};
-    registry.register(target, {});
-    eval("");
-}
-
 test("basic functionality", () => {
     expect(WeakMap.prototype.set).toHaveLength(2);
 
@@ -27,26 +21,25 @@ test("invalid values", () => {
     });
 });
 
-function setObjectKey(weakMap) {
-    expect(weakMap.set({ e: 3 }, 1)).toBe(weakMap);
-}
-
-function setSymbolKey(weakMap) {
-    expect(weakMap.set(Symbol("foo"), "bar")).toBe(weakMap);
-}
-
 test("automatic removal of garbage-collected values", () => {
     const weakMap = new WeakMap();
+    const objectKey = { e: 3 };
 
-    setObjectKey(weakMap);
+    expect(weakMap.set(objectKey, 1)).toBe(weakMap);
     expect(getWeakMapSize(weakMap)).toBe(1);
 
+    markAsGarbage("objectKey");
     gc();
+
     expect(getWeakMapSize(weakMap)).toBe(0);
 
-    setSymbolKey(weakMap);
+    const symbolKey = Symbol("foo");
+
+    expect(weakMap.set(symbolKey, "bar")).toBe(weakMap);
     expect(getWeakMapSize(weakMap)).toBe(1);
 
+    markAsGarbage("symbolKey");
     gc();
+
     expect(getWeakMapSize(weakMap)).toBe(0);
 });

Userland/Libraries/LibJS/Tests/builtins/WeakSet/WeakSet.prototype.add.js

@@ -16,26 +16,25 @@ test("invalid values", () => {
     });
 });
 
-function addObjectItem(weakSet) {
-    weakSet.add({ a: 1 });
-}
-
-function addSymbolItem(weakSet) {
-    weakSet.add(Symbol("foo"));
-}
-
 test("automatic removal of garbage-collected values", () => {
     const weakSet = new WeakSet();
+    const objectItem = { a: 1 };
 
-    addObjectItem(weakSet);
+    expect(weakSet.add(objectItem)).toBe(weakSet);
     expect(getWeakSetSize(weakSet)).toBe(1);
 
+    markAsGarbage("objectItem");
     gc();
+
     expect(getWeakSetSize(weakSet)).toBe(0);
 
-    addSymbolItem(weakSet);
+    const symbolItem = Symbol("foo");
+
+    expect(weakSet.add(symbolItem)).toBe(weakSet);
     expect(getWeakSetSize(weakSet)).toBe(1);
 
+    markAsGarbage("symbolItem");
     gc();
+
     expect(getWeakSetSize(weakSet)).toBe(0);
 });