[NativeFS] Keep directory iterator alive while it has pending promises.

Should hopefully also fix test flakiness where tests seemed to already
be running into this.

Fixed: 1074123
Change-Id: If57c8d6f622c17d795bc1429f66485cda94befd2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2313763Reviewed-by: Victor Costan <pwnall@chromium.org>
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791122}

third_party/blink/renderer/modules/native_file_system/native_file_system_directory_iterator.cc

@@ -68,6 +68,10 @@ ScriptPromise NativeFileSystemDirectoryIterator::next(
   return ScriptPromise::Cast(script_state, V8IteratorResultDone(script_state));
 }
 
+bool NativeFileSystemDirectoryIterator::HasPendingActivity() const {
+  return pending_next_;
+}
+
 void NativeFileSystemDirectoryIterator::Trace(Visitor* visitor) const {
   ScriptWrappable::Trace(visitor);
   ExecutionContextClient::Trace(visitor);

third_party/blink/renderer/modules/native_file_system/native_file_system_directory_iterator.h

@@ -8,6 +8,7 @@
 #include "base/files/file.h"
 #include "third_party/blink/public/mojom/native_file_system/native_file_system_directory_handle.mojom-blink.h"
 #include "third_party/blink/public/mojom/native_file_system/native_file_system_error.mojom-blink.h"
+#include "third_party/blink/renderer/bindings/core/v8/active_script_wrappable.h"
 #include "third_party/blink/renderer/core/execution_context/execution_context_lifecycle_observer.h"
 #include "third_party/blink/renderer/platform/bindings/script_wrappable.h"
 #include "third_party/blink/renderer/platform/mojo/heap_mojo_receiver.h"
@@ -22,6 +23,7 @@ class ScriptState;
 
 class NativeFileSystemDirectoryIterator final
     : public ScriptWrappable,
+      public ActiveScriptWrappable<NativeFileSystemDirectoryIterator>,
       public ExecutionContextClient,
       public mojom::blink::NativeFileSystemDirectoryEntriesListener {
   DEFINE_WRAPPERTYPEINFO();
@@ -37,6 +39,9 @@ class NativeFileSystemDirectoryIterator final
 
   ScriptPromise next(ScriptState*);
 
+  // ScriptWrappable:
+  bool HasPendingActivity() const final;
+
   void Trace(Visitor*) const override;
 
  private:

third_party/blink/renderer/modules/native_file_system/native_file_system_directory_iterator.idl

@@ -7,6 +7,7 @@
 // https://www.ecma-international.org/ecma-262/9.0/index.html#sec-asynciterator-interface
 [
     NoInterfaceObject,
+    ActiveScriptWrappable,
     RuntimeEnabled=NativeFileSystem
 ] interface NativeFileSystemDirectoryIterator {
   [CallWith=ScriptState] Promise<any> next();

third_party/blink/web_tests/external/wpt/native-file-system/script-tests/FileSystemDirectoryHandle-iteration.js

@@ -78,3 +78,21 @@ directory_test(async (t, root) => {
   names.sort();
   assert_array_equals(names, [file_name1, file_name2]);
 }, 'keys: full iteration works');
+
+directory_test(async (t, root) => {
+  const file_name1 = 'foo1.txt';
+  await createFileWithContents(t, file_name1, 'contents', /*parent=*/ root);
+
+  const next = (() => {
+    const iterator = root.entries();
+    return iterator.next();
+  })();
+  garbageCollect();
+  let entry = await next;
+  assert_false(entry.done);
+  assert_true(Array.isArray(entry.value));
+  assert_equals(entry.value.length, 2);
+  assert_equals(entry.value[0], file_name1);
+  assert_true(entry.value[1] instanceof FileSystemFileHandle);
+  assert_equals(entry.value[1].name, file_name1);
+}, 'iteration while iterator gets garbage collected');