Chrome Cleaner: Remove indirect base::FilePath mojo dependency.

The dependency on mojo.common.mojom.FilePath resolves to base::FilePath
through a [Native] typemap. The Chrome cleaner is an independent binary
whose version of base::FilePath will diverge from Chrome's base::FilePath,
causing compatibility issues down the line.

This will also allow the Chrome Cleaner project to set
enable_mojom_typemapping to false.

BUG=

Review-Url: https://codereview.chromium.org/2932703006
Cr-Commit-Position: refs/heads/master@{#479471}
7 files changed