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- Creates a free form SMB share dialog
- Dialog will be opened by SmbProvider::RequestMount

Bug: chromium:887135
Change-Id: I379417ac15d633bce704bd50c8d31e8488fc2975
Reviewed-on: https://chromium-review.googlesource.com/c/1289409
Commit-Queue: Bailey Berro <baileyberro@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607008}