Changes places where we explicitly construct an Optional to instead use nullopt or the requisite value type only. This CL was uploaded by git cl split. R=mbonadei@webrtc.org Bug: None Change-Id: Iec336d342414dc68b59ba4b4623fdf768f6fb655 Reviewed-on: https://webrtc-review.googlesource.com/23602 Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org> Commit-Queue: Oskar Sundbom <ossu@webrtc.org> Cr-Commit-Position: refs/heads/master@{#20932}