LibWeb/IndexedDB: Prevent copying and moving of RequestList

RequestList cannot be copied or moved, because m_pending_request_queue
contains lambdas that store pointers to the original RequestList and
completion steps that we don't have a reference to.

Fixes a bunch of WPT regressions and imports the ones that work.

Tests/LibWeb/Text/input/wpt-import/IndexedDB/idbcursor-request-source.any.js

@@ -0,0 +1,116 @@
+// META: global=window,worker
+// META: title=IndexedDB: The source of requests made against cursors
+// META: script=resources/support.js
+
+// Spec: https://w3c.github.io/IndexedDB/#dom-idbrequest-source
+
+'use strict';
+
+// Setup each test by populating an object store with an index for the cursor to
+// iterate and manipulate.
+function initializeDatabase(db) {
+  const store = db.createObjectStore('store', {autoIncrement: true});
+  store.createIndex('index', /*keypath=*/ 'value');
+  store.put({value: 'z'});
+  store.put({value: 'y'});
+  store.put({value: 'x'});
+  store.put({value: 'w'});
+}
+
+function isIndex(cursorSourceType) {
+  return cursorSourceType === 'IDBIndex';
+}
+
+// Return the object store or index, depending on the test's `cursorSourceType`.
+function getCursorSource(transaction, cursorSourceType) {
+  let cursorSource = transaction.objectStore('store');
+  if (isIndex(cursorSourceType)) {
+    cursorSource = cursorSource.index('index');
+  }
+  return cursorSource;
+}
+
+// Verify the request source after calling delete() or update() on the cursor.
+function cursor_request_source_test(
+    cursorSourceType, createRequestFunctionName, createRequestFunctionArgs) {
+  indexeddb_test(
+      (t, db) => initializeDatabase(db),
+      (t, db) => {
+        const tx = db.transaction('store', 'readwrite');
+        const cursorSource = getCursorSource(tx, cursorSourceType);
+
+        // Open the cursor.
+        const openCursorRequest = cursorSource.openCursor();
+        openCursorRequest.onerror =
+            t.unreached_func('The cursor must not fail to open.');
+
+        openCursorRequest.onsuccess = t.step_func(e => {
+          // Use the cursor to create a new request.
+          const cursor = e.target.result;
+          const request =
+              cursor[createRequestFunctionName](...createRequestFunctionArgs);
+          assert_equals(
+              request.source, cursor,
+              `The request's source must be the cursor itself.`);
+          t.done();
+        });
+      },
+      `The source of the request from ${cursorSourceType}::${
+          createRequestFunctionName}() is the cursor itself`);
+}
+
+// Verify the request source after calling openCursor() or openKeyCursor() and
+// then using the cursor to iterate.
+function open_cursor_request_source_test(
+    cursorSourceType, openCursorFunctionName) {
+  indexeddb_test(
+      (t, db) => initializeDatabase(db),
+      (t, db) => {
+        const tx = db.transaction('store', 'readonly');
+        const cursorSource = getCursorSource(tx, cursorSourceType);
+
+        // Open the cursor.
+        const openCursorRequest = cursorSource[openCursorFunctionName]();
+        openCursorRequest.onerror =
+            t.unreached_func('The cursor must not fail to open or iterate.');
+
+        assert_equals(
+            openCursorRequest.source, cursorSource,
+            'The request source must be the opener of the cursor.');
+
+        // Verify the cursor's `request.source` after iterating with
+        // `advance()`, `continue()`, and `continuePrimaryKey()`.
+        let iterationCount = 0;
+        openCursorRequest.onsuccess = t.step_func(e => {
+          assert_equals(
+              openCursorRequest.source, cursorSource,
+              'The request source must be the opener of the cursor after iterating.');
+
+          const cursor = e.target.result;
+          ++iterationCount;
+
+          if (iterationCount == 1) {
+            cursor.advance(1);
+          } else if (iterationCount == 2) {
+            cursor.continue();
+          } else if (iterationCount == 3 && isIndex(cursorSourceType)) {
+            cursor.continuePrimaryKey('z', 0);
+          } else {
+            t.done();
+          }
+        });
+      },
+      `${cursorSourceType}::${
+          openCursorFunctionName}'s request source must be the ${
+          cursorSourceType} instance that opened the cursor`);
+}
+
+open_cursor_request_source_test('IDBObjectStore', 'openCursor');
+open_cursor_request_source_test('IDBObjectStore', 'openKeyCursor');
+open_cursor_request_source_test('IDBIndex', 'openCursor');
+open_cursor_request_source_test('IDBIndex', 'openKeyCursor');
+
+cursor_request_source_test('IDBObjectStore', 'update', /*args=*/[0]);
+cursor_request_source_test('IDBObjectStore', 'delete', /*args=*/[]);
+cursor_request_source_test('IDBIndex', 'update', /*args=*/[0]);
+cursor_request_source_test('IDBIndex', 'delete', /*args=*/[]);