mediaview: Hack to avoid Files app to freeze soon after login.

chrome/browser/chromeos/arc/fileapi/arc_documents_provider_root.cc

Index: chrome/browser/chromeos/arc/fileapi/arc_documents_provider_root.cc
diff --git a/chrome/browser/chromeos/arc/fileapi/arc_documents_provider_root.cc b/chrome/browser/chromeos/arc/fileapi/arc_documents_provider_root.cc
index 6c8b936f1260af4f699518db8174efbc2b458cc8..6a65157662e298959d35312d7104c49e454c5527 100644
--- a/chrome/browser/chromeos/arc/fileapi/arc_documents_provider_root.cc
+++ b/chrome/browser/chromeos/arc/fileapi/arc_documents_provider_root.cc
@@ -26,6 +26,15 @@ namespace arc {
 
 namespace {
 
+// A special watcher ID indicating this watcher is orphaned.
+// Though we have an entry in ArcDocumentsProviderRoot, the remote
+// ArcFileSystemService does not have a corresponding watcher. This happens
+// when, for example, AddWatcher() is called for non-existent files or the
+// remote service crashes.
+// We use this value to allow RemoveWatcher() to succeed even after the remote
+// service forgets watchers.
+constexpr int64_t kOrphanWatcherId = -1;
+
 // Computes a file name for a document.
 // TODO(crbug.com/675868): Consolidate with the similar logic for Drive.
 base::FilePath::StringType GetFileNameForDocument(
@@ -102,20 +111,35 @@ void ArcDocumentsProviderRoot::AddWatcher(
     const WatcherCallback& watcher_callback,
     const StatusCallback& callback) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  if (path_to_watcher_id_.count(path)) {
+  if (path_to_watcher_id_.count(path) ||
+      path_to_watcher_request_id_.count(path)) {
     callback.Run(base::File::FILE_ERROR_FAILED);
     return;
   }
+  uint64_t watcher_request_id = next_watcher_request_id_++;
+  path_to_watcher_request_id_.insert(std::make_pair(path, watcher_request_id));
   ResolveToDocumentId(
-      path,
-      base::Bind(&ArcDocumentsProviderRoot::AddWatcherWithDocumentId,
-                 weak_ptr_factory_.GetWeakPtr(), path, watcher_callback,
-                 callback));
+      path, base::Bind(&ArcDocumentsProviderRoot::AddWatcherWithDocumentId,
+                       weak_ptr_factory_.GetWeakPtr(), path, watcher_request_id,
+                       watcher_callback));
+
+  // HACK: Invoke |callback| immediately.
+  //
+  // TODO(crbug.com/698624): Remove this hack. It was introduced because Files
+  // app freezes until AddWatcher() finishes, but it should be handled in Files
+  // app rather than here.
+  callback.Run(base::File::FILE_OK);
 }
 
 void ArcDocumentsProviderRoot::RemoveWatcher(const base::FilePath& path,
                                              const StatusCallback& callback) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  auto iter_request = path_to_watcher_request_id_.find(path);
+  if (iter_request != path_to_watcher_request_id_.end()) {
+    path_to_watcher_request_id_.erase(iter_request);
+    callback.Run(base::File::FILE_OK);
+    return;
+  }
   auto iter = path_to_watcher_id_.find(path);
   if (iter == path_to_watcher_id_.end()) {
     callback.Run(base::File::FILE_ERROR_FAILED);
@@ -149,7 +173,7 @@ void ArcDocumentsProviderRoot::OnWatchersCleared() {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   // Mark all watchers orphan.
   for (auto& entry : path_to_watcher_id_)
-    entry.second = -1;
+    entry.second = kOrphanWatcherId;
 }
 
 void ArcDocumentsProviderRoot::GetFileInfoWithDocumentId(
@@ -232,52 +256,56 @@ void ArcDocumentsProviderRoot::ReadDirectoryWithNameToThinDocumentMap(
 
 void ArcDocumentsProviderRoot::AddWatcherWithDocumentId(
     const base::FilePath& path,
+    uint64_t watcher_request_id,
     const WatcherCallback& watcher_callback,
-    const StatusCallback& callback,
     const std::string& document_id) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
+
+  if (IsWatcherRequestCanceled(path, watcher_request_id))
+    return;
+
   if (document_id.empty()) {
-    callback.Run(base::File::FILE_ERROR_NOT_FOUND);
+    DCHECK(!path_to_watcher_id_.count(path));
+    path_to_watcher_id_.insert(std::make_pair(path, kOrphanWatcherId));
+    path_to_watcher_request_id_.erase(path);
     return;
   }
+
   // Start observing ArcFileSystemOperationRunner if we have not.
   if (!observer_wrapper_) {
     observer_wrapper_ =
         new file_system_operation_runner_util::ObserverIOThreadWrapper(this);
     file_system_operation_runner_util::AddObserverOnIOThread(observer_wrapper_);
   }
+
   file_system_operation_runner_util::AddWatcherOnIOThread(
       authority_, document_id, watcher_callback,
       base::Bind(&ArcDocumentsProviderRoot::OnWatcherAdded,
-                 weak_ptr_factory_.GetWeakPtr(), path, callback));
+                 weak_ptr_factory_.GetWeakPtr(), path, watcher_request_id));
 }
 
 void ArcDocumentsProviderRoot::OnWatcherAdded(const base::FilePath& path,
-                                              const StatusCallback& callback,
+                                              uint64_t watcher_request_id,
                                               int64_t watcher_id) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  if (watcher_id < 0) {
-    callback.Run(base::File::FILE_ERROR_FAILED);
-    return;
-  }
-  if (path_to_watcher_id_.count(path)) {
-    // Multiple watchers have been installed on the same file path in a race.
-    // Following the contract of WatcherManager, we reject all except the first.
+
+  if (IsWatcherRequestCanceled(path, watcher_request_id)) {
     file_system_operation_runner_util::RemoveWatcherOnIOThread(
         watcher_id,
         base::Bind(&ArcDocumentsProviderRoot::OnWatcherAddedButRemoved,
-                   weak_ptr_factory_.GetWeakPtr(), callback));
+                   weak_ptr_factory_.GetWeakPtr()));
     return;
   }
-  path_to_watcher_id_.insert(std::make_pair(path, watcher_id));
-  callback.Run(base::File::FILE_OK);
+
+  DCHECK(!path_to_watcher_id_.count(path));
+  path_to_watcher_id_.insert(
+      std::make_pair(path, watcher_id < 0 ? kOrphanWatcherId : watcher_id));
+  path_to_watcher_request_id_.erase(path);
 }
 
-void ArcDocumentsProviderRoot::OnWatcherAddedButRemoved(
-    const StatusCallback& callback,
-    bool success) {
+void ArcDocumentsProviderRoot::OnWatcherAddedButRemoved(bool success) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  callback.Run(base::File::FILE_ERROR_FAILED);
+  // Ignore |success|.
 }
 
 void ArcDocumentsProviderRoot::OnWatcherRemoved(const StatusCallback& callback,
@@ -286,6 +314,14 @@ void ArcDocumentsProviderRoot::OnWatcherRemoved(const StatusCallback& callback,
   callback.Run(success ? base::File::FILE_OK : base::File::FILE_ERROR_FAILED);
 }
 
+bool ArcDocumentsProviderRoot::IsWatcherRequestCanceled(
+    const base::FilePath& path,
+    uint64_t watcher_request_id) {
+  auto iter = path_to_watcher_request_id_.find(path);
+  return (iter == path_to_watcher_request_id_.end() ||
+          iter->second != watcher_request_id);
+}
+
 void ArcDocumentsProviderRoot::ResolveToContentUrlWithDocumentId(
     const ResolveToContentUrlCallback& callback,
     const std::string& document_id) {