mandoline filesystem: add a sqlite3 vfs to proxy filesystem usage.

components/filesystem/file_impl.cc

Index: components/filesystem/file_impl.cc
diff --git a/components/filesystem/file_impl.cc b/components/filesystem/file_impl.cc
index f378432e724b8ca1226c76058ab315640c05fc3a..25394989477ad5a8641706d67f91a7f6724bf06e 100644
--- a/components/filesystem/file_impl.cc
+++ b/components/filesystem/file_impl.cc
@@ -260,6 +260,16 @@ void FileImpl::Dup(mojo::InterfaceRequest<File> file,
   callback.Run(FILE_ERROR_OK);
 }
 
+void FileImpl::Flush(const FlushCallback& callback) {
+  if (!file_.IsValid()) {
+    callback.Run(GetError(file_));
+    return;
+  }
+
+  bool ret = file_.Flush();
+  callback.Run(ret ? FILE_ERROR_OK : FILE_ERROR_FAILED);
+}
+
 void FileImpl::AsHandle(const AsHandleCallback& callback) {
   if (!file_.IsValid()) {
     callback.Run(GetError(file_), ScopedHandle());