Files.app: Set initial refresh command visibility false.
Files.app: Set initial refresh command visibility false.

This CL sets initial vibisility of refresh command false.
Along with it, toolbar button's visibility is hidden to take care of the period
from the timing toolbar button created to the timing the button is wired to the
refresh command.

BUG=508817
TEST=manually

Review URL: https://codereview.chromium.org/1232073002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#338246}

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