Google Chrome	61.0.3163.80 (Official Build) beta (64-bit)
Revision	0
Platform	9765.53.0 (Official Build) beta-channel caroline
Firmware Version	Google_Caroline.7820.316.0
Customization ID	SAMSUNG-CAROLINE
ARC	4312059
JavaScript	V8 6.1.534.32
Flash	27.0.0.130 

Samsung Chromebook Pro

Steps To Reproduce:
1) Connect to 4k 60Hz monitor via capable usb-c to hdmi adapter and cable, with monitor running at 2160p.
2) Open and attempt to use android app
3) 

Expected Result:
Apps should behave like they do on the normal screen

Actual Result:
Observe severe lag on any android app, but not chrome browser (eg fullscreen 4k youtube video plays fine in chrome browser and is unusably jerky at only 1440p in android app). For some reason turning down the display resolution in settings even a tiny bit to 1728p has huge performance improvements.

How frequently does this problem reproduce? (Always, sometimes, hard to
reproduce?)

Always

What is the impact to the user, and is there a workaround? If so, what is
it?

4k external monitors are basically unusable with android apps at native resolution.

Please provide any additional information below. Attach a screen shot or
log if possible.

For graphics-related bugs, please copy/paste the contents of the about:gpu
page at the end of this report.

Graphics Feature Status
Canvas: Hardware accelerated
CheckerImaging: Disabled
Flash: Hardware accelerated
Flash Stage3D: Hardware accelerated
Flash Stage3D Baseline profile: Hardware accelerated
Compositing: Hardware accelerated
Multiple Raster Threads: Enabled
Native GpuMemoryBuffers: Hardware accelerated
Panel Fitting: Unavailable
Rasterization: Hardware accelerated
Video Decode: Hardware accelerated
Video Encode: Hardware accelerated
WebGL: Hardware accelerated
WebGL2: Hardware accelerated
Driver Bug Workarounds
clear_uniforms_before_first_program_use
count_all_in_varyings_packing
decode_encode_srgb_for_generatemipmap
disable_discard_framebuffer
msaa_is_slow
scalarize_vec_and_mat_constructor_args
rely_on_implicit_sync_for_swap_buffers
Problems Detected
Chrome OS panel fitting is only supported for Intel IVB and SNB Graphics Controllers
Disabled Features: panel_fitting
Framebuffer discarding causes jumpy scrolling on Mali drivers: 301988
Applied Workarounds: disable_discard_framebuffer
Clear uniforms before first program use on all platforms: 124764, 349137
Applied Workarounds: clear_uniforms_before_first_program_use
Mesa drivers in ChromeOS handle varyings without static use incorrectly: 333885
Applied Workarounds: count_all_in_varyings_packing
Always rewrite vec/mat constructors to be consistent: 398694
Applied Workarounds: scalarize_vec_and_mat_constructor_args
On Intel GPUs MSAA performance is not acceptable for GPU rasterization: 527565
Applied Workarounds: msaa_is_slow
Disable KHR_blend_equation_advanced until cc shaders are updated: 661715
Decode and Encode before generateMipmap for srgb format textures on Chromeos Intel: 634519
Applied Workarounds: decode_encode_srgb_for_generatemipmap
Avoid waiting on a egl fence before pageflipping and rely on implicit sync.: 721463
Applied Workarounds: rely_on_implicit_sync_for_swap_buffers
Checker-imaging has been disabled via finch trial or the command line.
Disabled Features: checker_imaging