[fsp] Add support for observing entries and notifying about changes.

chrome/browser/chromeos/extensions/file_system_provider/file_system_provider_api.cc

Index: chrome/browser/chromeos/extensions/file_system_provider/file_system_provider_api.cc
diff --git a/chrome/browser/chromeos/extensions/file_system_provider/file_system_provider_api.cc b/chrome/browser/chromeos/extensions/file_system_provider/file_system_provider_api.cc
index e8fafd7a408e200fda0571cb05feca3f1e2da6da..9f83258f2b4cff14e6e5ea54ad24cd0bbe058faf 100644
--- a/chrome/browser/chromeos/extensions/file_system_provider/file_system_provider_api.cc
+++ b/chrome/browser/chromeos/extensions/file_system_provider/file_system_provider_api.cc
@@ -24,6 +24,13 @@ using chromeos::file_system_provider::RequestValue;
 using chromeos::file_system_provider::Service;
 
 namespace extensions {
+namespace {
+
+const char kNotifyFailedErrorMessage[] =
+    "Sending a response for the request failed.";
+const char kInvalidNotificationErrorMessage[] = "The notification is invalid.";
+
+}  // namespace
 
 bool FileSystemProviderMountFunction::RunSync() {
   using api::file_system_provider::Mount::Params;
@@ -56,7 +63,8 @@ bool FileSystemProviderMountFunction::RunSync() {
   if (!service->MountFileSystem(extension_id(),
                                 params->options.file_system_id,
                                 params->options.display_name,
-                                params->options.writable)) {
+                                params->options.writable,
+                                params->options.supports_notify_tag)) {

[mtomasz, 2014/10/03 04:22:47]

If a file system supports_notify_tag is |true|, then when calling
chrome.fileSystemProvider.Notify |tag| must be provided, too.

The tag can be eg. a revision number for Drive notifications. The purpose of it
is to never miss any notifications, eg.:

1. Drive providing extension notifies about a /hoge-fuka.txt file being changed,
with a tag "123".
2. Chromebook is shutdown.
3. A lot of files are changed. No notification emited, because computer is off.
4. Chromebook is resumed.
5. Drive providing extension emits all notifications which happened since tag
"123".

Without tags, we can't provide continuous notifications when the computer is
off, or internet is off. Drive provides a changeId field, which can be used as
tag. Dropbox provides a tag too.

Note, that extensions may not provide a tag. If not, then notifications may not
arrive when the computer is off, or internet is off. Caching needs reliable
notifications about changes, in order to invalidate changed files. Hence, we
will enable caching only if supports_notify_tag is true.

     base::ListValue* const result = new base::ListValue();
     result->Append(CreateError(kSecurityErrorName, kMountFailedErrorMessage));
     SetResult(result);
@@ -116,6 +124,46 @@ bool FileSystemProviderGetAllFunction::RunSync() {
   return true;
 }
 
+bool FileSystemProviderNotifyFunction::RunSync() {
+  using api::file_system_provider::Notify::Params;
+  scoped_ptr<Params> params(Params::Create(*args_));
+  EXTENSION_FUNCTION_VALIDATE(params);
+
+  Service* const service = Service::Get(GetProfile());
+  DCHECK(service);
+  if (!service)
+    return false;
+
+  ProvidedFileSystemInterface* const file_system =
+      service->GetProvidedFileSystem(extension_id(),
+                                     params->options.file_system_id);
+  if (!file_system) {
+    base::ListValue* const result = new base::ListValue();
+    result->Append(CreateError(kNotFoundErrorName, kNotifyFailedErrorMessage));
+    SetResult(result);
+    return true;
+  }
+
+  // TODO(mtomasz): Pass real data to Notify() instead of fake ones.
+  if (!file_system->Notify(

[mtomasz, 2014/10/03 04:22:47]

This is not used yet.

+          base::FilePath::FromUTF8Unsafe(params->options.observed_path),
+          chromeos::file_system_provider::ProvidedFileSystemObserver::
+              CHANGED,
+          chromeos::file_system_provider::ProvidedFileSystemObserver::
+              ChildChanges(),
+          "todo-tag")) {
+    base::ListValue* const result = new base::ListValue();
+    result->Append(
+        CreateError(kSecurityErrorName, kInvalidNotificationErrorMessage));
+    SetResult(result);
+    return true;
+  }
+
+  base::ListValue* const result = new base::ListValue();
+  SetResult(result);
+  return true;
+}
+
 bool FileSystemProviderInternalUnmountRequestedSuccessFunction::RunWhenValid() {
   using api::file_system_provider_internal::UnmountRequestedSuccess::Params;
   scoped_ptr<Params> params(Params::Create(*args_));