Your system information

Computer Information:
    Manufacturer:  Unknown
    Model:  Unknown
    Form Factor: Desktop
    No Touch Input Detected

Processor Information:
    CPU Vendor:  GenuineIntel
    CPU Brand:  Intel(R) Core(TM) i7-7700K CPU @ 4.20GHz
    CPU Family:  0x6
    CPU Model:  0x9e
    CPU Stepping:  0x9
    CPU Type:  0x0
    Speed:  4500 Mhz
    8 logical processors
    4 physical processors
    HyperThreading:  Supported
    FCMOV:  Supported
    SSE2:  Supported
    SSE3:  Supported
    SSSE3:  Supported
    SSE4a:  Unsupported
    SSE41:  Supported
    SSE42:  Supported
    AES:  Supported
    AVX:  Supported
    CMPXCHG16B:  Supported
    LAHF/SAHF:  Supported
    PrefetchW:  Unsupported

Operating System Version:
    Debian GNU/Linux testing (buster) (64 bit)
    Kernel Name:  Linux
    Kernel Version:  4.13.7
    X Server Vendor:  The X.Org Foundation
    X Server Release:  11905000
    X Window Manager:  LG3D
    Steam Runtime Version:  steam-runtime-beta-release_2017-10-05

Video Card:
    Driver:  NVIDIA Corporation GeForce GTX 1070/PCIe/SSE2
    Driver Version:  4.6.0 NVIDIA 387.34
    OpenGL Version: 4.6
    Desktop Color Depth: 24 bits per pixel
    Monitor Refresh Rate: 59 Hz
    VendorID:  0x10de
    DeviceID:  0x1b81
    Revision Not Detected
    Number of Monitors:  1
    Number of Logical Video Cards:  1
    Primary Display Resolution:  1920 x 1200
    Desktop Resolution: 1920 x 1200
    Primary Display Size: 21.50" x 13.86" (25.55" diag)
                                            54.6cm x 35.2cm (64.9cm diag)
    Primary Bus: PCI Express 16x
    Primary VRAM: 8192 MB
    Supported MSAA Modes:  2x 4x 8x 16x 

Sound card:
    Audio device: Realtek ALC887-VD

Memory:
    RAM:  16013 Mb

Miscellaneous:
    UI Language:  English
    LANG:  en_GB.UTF-8
    Total Hard Disk Space Available:  240237 Mb
    Largest Free Hard Disk Block:  49770 Mb
    VR Headset: None detected

Recent Failure Reports:

• Steam client version (build number or date): 1513870789
• Distribution (e.g. Ubuntu): Debian buster/sid amd64
• Opted into Steam client beta?: Yes
• Have you checked for system updates?: Yes

Please describe your issue in as much detail as possible:

This is a continuation of #3699 actually. The video is now properly stretched horizontally but the top part is not being redrawn. The window actually covers the whole screen, when I click at that empty space on top it's being paused and resumed. My screen resolution is 1920x1200, not 1920x1080, and the distance between the screen top and the video area seems to be exactly 120 pixels.

Steps for reproducing this issue:

1. Have a 1920x1200 display
2. Open any game video in the Steam Store (a trailer or so, not a movie)
3. The window occupies the whole screen but it's only being redrawn at the bottom part, the top 120 lines are not repainted and usually contain part of the desktop image or other windows, tecnhically it's not being invalidated

I'm using AwesomeWM as window manager. I tested the issue on two machines, home and work, the main difference is the screen resolution. It only happens at home on 1920x1200 and absolutely fine at work on 1920x1080. Both machines use AwesomeWM, have NVIDIA GPUs and same version of Debian.