Update to Chrome 54.0.2840.99 in v54

[cztomczak]

CEF commit:
https://bitbucket.org/chromiumembedded/cef/commits/48e5f3d239cb5c086f75917acd4f21de6fb263f1

Key changes in upstream CEF between commits 7fe3d03...ffd843c (since CEF Python 54.0):

• Update to Chromium version 54.0.2840.99
• Fix PDF rendering with OSR
• Add CefRequestHandler::OnSelectClientCertificate (allows for client certificate selection programmatically)
• Fix load error when using Request->SetUrl when url contains double byte characters
• Fix crash related to channel ID support, disable channel ID support
• Net security (CT, HSTS) expiration based on build age is now disabled by default. Configurable with CefSettings.enable_net_security_expiration.
• New web plugin API: CefRegisterCdmCallback, CefRegisterWidevineCdm

[cztomczak]

Done in commits 1da0110 and 2f336cf.