GitLab

- Added SandboxType::kMediaFoundationCdm and its corresponding sandbox
  switch of "mf_cdm" for the creation of MF Cdm LPAC Utility process.
- SandboxWin::IsAppContainerEnabledForSandbox() is updated to opt-in
  SandboxType::kMediaFoundationCdm to be created as AppContainer
  process.
- In SandboxWin::StartSandboxedProcess(), the MF Cdm is added with
  policies and LPAC capabilities to allow existing Windows platform
  compoenents to work properly.

More details can be found in this doc:
https://docs.google.com/document/d/19Y4Js5v3BlzA5uSuiVTvcvPNIOwmxcMSFJWtuc1A-w8/edit#heading=h.iqvhsrml3gl9

Bug: 999747
Change-Id: I8e0a0febb20b697c5631cf2561429305bf47b2e9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2401506
Commit-Queue: Frank Li <frankli@microsoft.com>
Reviewed-by: Will Harris <wfh@chromium.org>
Reviewed-by: Alex Gough <ajgo@chromium.org>
Reviewed-by: James Forshaw <forshaw@chromium.org>
Reviewed-by: Xiaohan Wang <xhwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#812187}