Add DriveFileSyncClient::IsAuthenticated

chrome/browser/sync_file_system/drive_file_sync_client.h

Index: chrome/browser/sync_file_system/drive_file_sync_client.h
diff --git a/chrome/browser/sync_file_system/drive_file_sync_client.h b/chrome/browser/sync_file_system/drive_file_sync_client.h
index e2b43f6f8b746caa12f6e5e12b4fe1689018c668..48043d69bcc80bfe75adc49ee2ef2236e87d00c3 100644
--- a/chrome/browser/sync_file_system/drive_file_sync_client.h
+++ b/chrome/browser/sync_file_system/drive_file_sync_client.h
@@ -136,6 +136,11 @@ class DriveFileSyncClient : public base::NonThreadSafe,
                           int64 file_size,
                           const UploadFileCallback& callback);
 
+  // Returns true if the user is authenticated.
+  bool IsAuthenticated() const {
+    return drive_service_->HasRefreshToken();
+  }
+
   // Deletes the file identified by |resource_id|.
   // |remote_file_md5| represents the expected hash value of the file to be
   // deleted from Drive. If |remote_file_md5| is different from the actual