drive: Return cancel closure from FileSystem::GetFileContent

chrome/browser/chromeos/drive/file_system.cc

Index: chrome/browser/chromeos/drive/file_system.cc
diff --git a/chrome/browser/chromeos/drive/file_system.cc b/chrome/browser/chromeos/drive/file_system.cc
index 3d1fad1903947516f8849bda3517115e29e0b8e7..4e67ffad4ad4d91ee91dff32ccdacf842793b0eb 100644
--- a/chrome/browser/chromeos/drive/file_system.cc
+++ b/chrome/browser/chromeos/drive/file_system.cc
@@ -612,7 +612,7 @@ void FileSystem::GetFileForSaving(const base::FilePath& file_path,
   get_file_for_saving_operation_->GetFileForSaving(file_path, callback);
 }
 
-void FileSystem::GetFileContent(
+base::Closure FileSystem::GetFileContent(
     const base::FilePath& file_path,
     const GetFileContentInitializedCallback& initialized_callback,
     const google_apis::GetContentCallback& get_content_callback,
@@ -622,7 +622,7 @@ void FileSystem::GetFileContent(
   DCHECK(!get_content_callback.is_null());
   DCHECK(!completion_callback.is_null());
 
-  download_operation_->EnsureFileDownloadedByPath(
+  return download_operation_->EnsureFileDownloadedByPath(
       file_path,
       ClientContext(USER_INITIATED),
       initialized_callback,