[Linux, Media Gallery] Fix MTPRecursiveDeviceObjectEnumerator to recursively enumerate all the medi…

chrome/browser/media_gallery/linux/mtp_recursive_device_object_enumerator.cc

Index: chrome/browser/media_gallery/linux/mtp_recursive_device_object_enumerator.cc
diff --git a/chrome/browser/media_gallery/linux/mtp_recursive_device_object_enumerator.cc b/chrome/browser/media_gallery/linux/mtp_recursive_device_object_enumerator.cc
index 2b5ceebea0759b0b0c5e0735df5953bbf83c3388..41584bb51fde27c00ed77fe5d790d60203d79b1e 100644
--- a/chrome/browser/media_gallery/linux/mtp_recursive_device_object_enumerator.cc
+++ b/chrome/browser/media_gallery/linux/mtp_recursive_device_object_enumerator.cc
@@ -19,13 +19,14 @@ MTPRecursiveDeviceObjectEnumerator::MTPRecursiveDeviceObjectEnumerator(
     base::WaitableEvent* shutdown_event)
     : device_handle_(handle),
       media_task_runner_(task_runner),
-      file_entries_(entries),
-      file_entry_iter_(file_entries_.begin()),
       on_task_completed_event_(task_completed_event),
       on_shutdown_event_(shutdown_event) {
   DCHECK(on_task_completed_event_);
   DCHECK(on_shutdown_event_);
+  DCHECK(!entries.empty());
   current_enumerator_.reset(new MTPDeviceObjectEnumerator(entries));
+  empty_enumerator_.reset(
+      new fileapi::FileSystemFileUtil::EmptyFileEnumerator());
 }
 
 MTPRecursiveDeviceObjectEnumerator::~MTPRecursiveDeviceObjectEnumerator() {
@@ -37,43 +38,56 @@ FilePath MTPRecursiveDeviceObjectEnumerator::Next() {
     return FilePath();
   }
 
-  FilePath path = current_enumerator_->Next();
-  if (!path.empty())
-    return path;
-
-  // We reached the end.
-  if (file_entry_iter_ == file_entries_.end())
+  if (!current_enumerator_)
     return FilePath();
 
-  // Enumerate subdirectories of the next media file entry.
-  MtpFileEntry next_file_entry = *file_entry_iter_;
-  ++file_entry_iter_;
+  if (!current_enumerator_->HasMoreEntries())
+    current_enumerator_ = GetSubdirectoryEnumerator();
 
-  // Create a MTPReadDirectoryWorker object to enumerate sub directories.
-  scoped_refptr<MTPReadDirectoryWorker> worker(new MTPReadDirectoryWorker(
-      device_handle_, next_file_entry.item_id(), media_task_runner_,
-      on_task_completed_event_, on_shutdown_event_));
-  worker->Run();
-  if (!worker->get_file_entries().empty()) {
-    current_enumerator_.reset(
-        new MTPDeviceObjectEnumerator(worker->get_file_entries()));
-  } else {
-    current_enumerator_.reset(
-        new fileapi::FileSystemFileUtil::EmptyFileEnumerator());
+  if (IsDirectory()) {
+    // If the current entry is a directory, add it to
+    // |untraversed_directory_entry_ids_| to scan after scanning this directory.
+    DirectoryEntryId dir_entry_id;
+    if (current_enumerator_->GetEntryId(&dir_entry_id))
+      untraversed_directory_entry_ids_.push(dir_entry_id);
   }
-  return current_enumerator_->Next();
+  return current_enumerator_ ?
+      current_enumerator_->Next() : empty_enumerator_->Next();
 }
 
 int64 MTPRecursiveDeviceObjectEnumerator::Size() {
-  return current_enumerator_->Size();
+  return current_enumerator_ ?
+      current_enumerator_->Size() : empty_enumerator_->Size();
 }
 
 bool MTPRecursiveDeviceObjectEnumerator::IsDirectory() {
-  return current_enumerator_->IsDirectory();
+  return current_enumerator_ ?
+      current_enumerator_->IsDirectory() : empty_enumerator_->IsDirectory();
 }
 
 base::Time MTPRecursiveDeviceObjectEnumerator::LastModifiedTime() {
-  return current_enumerator_->LastModifiedTime();
+  return current_enumerator_ ? current_enumerator_->LastModifiedTime() :
+      empty_enumerator_->LastModifiedTime();
+}
+
+scoped_ptr<MTPDeviceObjectEnumerator> MTPRecursiveDeviceObjectEnumerator::
+GetSubdirectoryEnumerator() {
+  while (!untraversed_directory_entry_ids_.empty()) {
+    // Create a MTPReadDirectoryWorker object to enumerate sub directories.
+    DirectoryEntryId dir_entry_id = untraversed_directory_entry_ids_.front();
+    untraversed_directory_entry_ids_.pop();
+    scoped_refptr<MTPReadDirectoryWorker> worker(new MTPReadDirectoryWorker(
+        device_handle_, dir_entry_id, media_task_runner_,
+        on_task_completed_event_, on_shutdown_event_));
+    worker->Run();
+    if (!worker->get_file_entries().empty()) {
+      return scoped_ptr<MTPDeviceObjectEnumerator>(
+          new MTPDeviceObjectEnumerator(worker->get_file_entries()));
+    }
+  }
+
+  // Reached the end. Traversed all the sub directories.
+  return scoped_ptr<MTPDeviceObjectEnumerator>();
 }
 
 }  // namespace chrome