Merge M51: Add base::IsOnNetworkDrive.

BUG=572131,606622
TEST=base_unittests
TEST=http://pastebin.com/raw/jNUNwiQe

Review URL: https://codereview.chromium.org/1892153003

Cr-Commit-Position: refs/heads/master@{#387981}
(cherry picked from commit 2396e07db179be4f5a22ab2acc1503d0cdb1e499)

Review URL: https://codereview.chromium.org/1917893004 .

Cr-Commit-Position: refs/branch-heads/2704@{#240}
Cr-Branched-From: 6e53600def8f60d8c632fadc70d7c1939ccea347-refs/heads/master@{#386251}
3 files changed