Chromium GPU support on Manjaro

[krist]

Hi everyone!                                                                                             
                                                                                                         
I've tried to enable GPU support and hardware video decoding in Chromium on Manjaro using the flags found in the Wiki. While they indeed make chrome://gpu show "Hardware accelerated" for most of the grahics sub-systems, they actually cause Chromium to run slower and more sluggish than without. And hardware-based video decoding still doesn't work, chrome://media-internals shows it's using a software decoder nonetheless.

I was almost ready to accept that having GPU suport in Chromium on Linux is just not really supported, even more so on ARM. Then I tried one of the ChromiumOS images (ayufan's R77) and much to my suprise, GPU support and hardware acceleration worked just fine! GL support, VP8/9 and MP4 hardware decoding - it just worked and Chromium also felt faster all around. From chrome://gpu :                                       
                                                                                                         
Manjaro:
GPU0  VENDOR= 0x0000 [VMware, Inc.], DEVICE=0x0000 [llvmpipe (LLVM 9.0.1, 128 bits)] *ACTIVE*

ChromiumOS:
GPU0  VENDOR = 0x0000 [ARM], DEVICE= 0x0000 [Mali-T860] *ACTIVE*                                         

Can somebody shed some light on why GPU support works fine in ChromiumOS but not in Manjaro? Which (kernel?) patches, drivers, config, flags do make the difference here?
                                                                                                         
(Note that apart from Chromium, hw decoding works just fine for me in Manjaro using mpv for example.)    

Thanks,                                                                                                  
krist