Mojo C++ bindings: switch components/filesystem mojom target to use STL types.

BUG=624136
[email protected] for trivial changes outside of filesystem and leveldb

Review-Url: https://codereview.chromium.org/2492283002
Cr-Commit-Position: refs/heads/master@{#431959}
15 files changed