1. Pass CdmConfig to CreatePlatformBrowserCdm.
2. Add |force_software_crypto| to AddChromecastKeySystems. When enable,
cast should use software based OEMCrypto in Widevine.
The CL just adds the parameter to the function, corresponding action
isn't added.
BUG=internal b/31575507
TEST=None
Review-Url: https://codereview.chromium.org/2478453002
Cr-Commit-Position: refs/heads/master@{#429668}