[Fuchsia] Make unsafe FidlInterfaceRequest constructor more explicit

Replace unsafe FildInterfaceRequest constructor with a static
FildInterfaceRequest::CreateFromChannelUnsafe().

Change-Id: I567588b3aabcc107e8197e2192124865ba5e959f
Reviewed-on: https://chromium-review.googlesource.com/1127468
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573075}
3 files changed