Unable to reproduce the issue on Stable 52.0.2743.116, Beta 53.0.2785.34 and canary 54.0.2817.0 on Mac 10.11.6.Could you please review the attached screenc ast and let us know if any.

Deleted: 634103_Aug_4.mp4 1021 KB

	634103_Aug_4.mp4 1021 KB View Download

I tried reproducing on a couple more macs with Chrome 53.0.2785.34.  One is an older macbook air running an Intel HD 3000, and it _does not_ reproduce the issue.  One is a bit newer than that, running an Intel HD 5000, and it _does_ reproduce the issue.  Both are running OSX 10.11.6.

Given that there are differences between machines, that may suggest this is a hardware-dependent problem of some sort.  

Eric or Chris, can you take a look?

Submitter: have you tested with Chrome Canary? Does the problem reproduce there, or only on Chrome Beta? I can't reproduce on a MacBook Air with Intel HD 5000 GPU with Canary.

Given that this is a relatively small UI problem I'm not inclined to investigate it on the beta branch. If you could start testing with Canary or Dev Channel, it's much easier for us to reproduce bugs against those branches/releases and fix them promptly.

It does not reproduce in 54.0.2819.0 (Official Build) canary (64-bit).  Your suggestion about running Canary has been noted for the future.

I attempted to reproduce this with 53.0.2785.46 (Official Build) beta (64-bit) on the abovementioned hardware (about:gpu below) and was not able to reproduce the flash of the canvas.

Graphics Feature Status
Canvas: Hardware accelerated
Flash: Hardware accelerated
Flash Stage3D: Hardware accelerated
Flash Stage3D Baseline profile: Hardware accelerated
Compositing: Hardware accelerated
Multiple Raster Threads: Enabled
Native GpuMemoryBuffers: Hardware accelerated
Rasterization: Software only. Hardware acceleration disabled
Video Decode: Hardware accelerated
Video Encode: Hardware accelerated
WebGL: Hardware accelerated
Driver Bug Workarounds
disable_framebuffer_cmaa
disable_multimonitor_multisampling
disable_webgl_rgb_multisampling_usage
init_varyings_without_static_use
msaa_is_slow
pack_parameters_workaround_with_pack_buffer
regenerate_struct_names
scalarize_vec_and_mat_constructor_args
set_zero_level_before_generating_mipmap
swizzle_rgba_for_async_readpixels
unfold_short_circuit_as_ternary_operation
unpack_alignment_workaround_with_unpack_buffer
use_intermediary_for_copy_texture_image
use_shadowed_tex_level_params
validate_multisample_buffer_allocation
Problems Detected
Async Readpixels with GL_BGRA format is broken on Haswell chipset on Macs: 265115
Applied Workarounds: swizzle_rgba_for_async_readpixels
Multisampling is buggy on OSX when multiple monitors are connected: 237931
Applied Workarounds: disable_multimonitor_multisampling
Multisampled renderbuffer allocation must be validated on some Macs: 290391
Applied Workarounds: validate_multisample_buffer_allocation
Unfold short circuit on Mac OS X: 307751
Applied Workarounds: unfold_short_circuit_as_ternary_operation
Mac drivers handle varyings without static use incorrectly: 322760
Applied Workarounds: init_varyings_without_static_use
Always rewrite vec/mat constructors to be consistent: 398694
Applied Workarounds: scalarize_vec_and_mat_constructor_args
Mac drivers handle struct scopes incorrectly: 403957
Applied Workarounds: regenerate_struct_names
On Intel GPUs MSAA performance is not acceptable for GPU rasterization: 527565
Applied Workarounds: msaa_is_slow
glGenerateMipmap fails if the zero texture level is not set on some Mac drivers: 560499
Applied Workarounds: set_zero_level_before_generating_mipmap
Pack parameters work incorrectly with pack buffer bound: 563714
Applied Workarounds: pack_parameters_workaround_with_pack_buffer
Alignment works incorrectly with unpack buffer bound: 563714
Applied Workarounds: unpack_alignment_workaround_with_unpack_buffer
copyTexImage2D fails when reading from IOSurface on multiple GPU types.: 581777
Applied Workarounds: use_intermediary_for_copy_texture_image
Multisample renderbuffers with format GL_RGB8 have performance issues on Intel GPUs.: 607130
Applied Workarounds: disable_webgl_rgb_multisampling_usage
Mac Drivers store texture level parameters on int16_t that overflow: 610153
Applied Workarounds: use_shadowed_tex_level_params
Limited enabling of Chromium GL_INTEL_framebuffer_CMAA: 535198
Applied Workarounds: disable_framebuffer_cmaa
Accelerated rasterization has been disabled, either via blacklist, about:flags or the command line.
Disabled Features: rasterization
Version Information
Data exported	8/4/2016, 5:35:00 PM
Chrome version	Chrome/53.0.2785.46
Operating system	Mac OS X 10.11.6
Software rendering list version	11.7
Driver bug list version	8.78
ANGLE commit id	c9e893119842
2D graphics backend	Skia
Command Line Args	Chrome.app/Contents/MacOS/Google Chrome -psn_0_110619 --flag-switches-begin --flag-switches-end
Driver Information
Initialization time	53
In-process GPU	false
Sandboxed	true
GPU0	VENDOR = 0x8086, DEVICE= 0x0a26
Optimus	false
AMD switchable	false
Driver vendor	
Driver version	10.14.73
Driver date	
Pixel shader version	1.20
Vertex shader version	1.20
Max. MSAA samples	8
Machine model name	MacBookAir
Machine model version	6.2
GL_VENDOR	Intel Inc.
GL_RENDERER	Intel HD Graphics 5000 OpenGL Engine
GL_VERSION	2.1 INTEL-10.14.73
GL_EXTENSIONS	GL_ARB_color_buffer_float GL_ARB_depth_buffer_float GL_ARB_depth_clamp GL_ARB_depth_texture GL_ARB_draw_buffers GL_ARB_draw_elements_base_vertex GL_ARB_draw_instanced GL_ARB_fragment_program GL_ARB_fragment_program_shadow GL_ARB_fragment_shader GL_ARB_framebuffer_object GL_ARB_framebuffer_sRGB GL_ARB_half_float_pixel GL_ARB_half_float_vertex GL_ARB_instanced_arrays GL_ARB_multisample GL_ARB_multitexture GL_ARB_occlusion_query GL_ARB_pixel_buffer_object GL_ARB_point_parameters GL_ARB_point_sprite GL_ARB_provoking_vertex GL_ARB_seamless_cube_map GL_ARB_shader_objects GL_ARB_shader_texture_lod GL_ARB_shading_language_100 GL_ARB_shadow GL_ARB_sync GL_ARB_texture_border_clamp GL_ARB_texture_compression GL_ARB_texture_compression_rgtc GL_ARB_texture_cube_map GL_ARB_texture_env_add GL_ARB_texture_env_combine GL_ARB_texture_env_crossbar GL_ARB_texture_env_dot3 GL_ARB_texture_float GL_ARB_texture_mirrored_repeat GL_ARB_texture_non_power_of_two GL_ARB_texture_rectangle GL_ARB_texture_rg GL_ARB_transpose_matrix GL_ARB_vertex_array_bgra GL_ARB_vertex_blend GL_ARB_vertex_buffer_object GL_ARB_vertex_program GL_ARB_vertex_shader GL_ARB_window_pos GL_EXT_abgr GL_EXT_bgra GL_EXT_blend_color GL_EXT_blend_equation_separate GL_EXT_blend_func_separate GL_EXT_blend_minmax GL_EXT_blend_subtract GL_EXT_clip_volume_hint GL_EXT_debug_label GL_EXT_debug_marker GL_EXT_draw_buffers2 GL_EXT_draw_range_elements GL_EXT_fog_coord GL_EXT_framebuffer_blit GL_EXT_framebuffer_multisample GL_EXT_framebuffer_multisample_blit_scaled GL_EXT_framebuffer_object GL_EXT_framebuffer_sRGB GL_EXT_geometry_shader4 GL_EXT_gpu_program_parameters GL_EXT_gpu_shader4 GL_EXT_multi_draw_arrays GL_EXT_packed_depth_stencil GL_EXT_packed_float GL_EXT_provoking_vertex GL_EXT_rescale_normal GL_EXT_secondary_color GL_EXT_separate_specular_color GL_EXT_shadow_funcs GL_EXT_stencil_two_side GL_EXT_stencil_wrap GL_EXT_texture_array GL_EXT_texture_compression_dxt1 GL_EXT_texture_compression_s3tc GL_EXT_texture_env_add GL_EXT_texture_filter_anisotropic GL_EXT_texture_integer GL_EXT_texture_lod_bias GL_EXT_texture_rectangle GL_EXT_texture_shared_exponent GL_EXT_texture_sRGB GL_EXT_texture_sRGB_decode GL_EXT_timer_query GL_EXT_transform_feedback GL_EXT_vertex_array_bgra GL_APPLE_aux_depth_stencil GL_APPLE_client_storage GL_APPLE_element_array GL_APPLE_fence GL_APPLE_float_pixels GL_APPLE_flush_buffer_range GL_APPLE_flush_render GL_APPLE_object_purgeable GL_APPLE_packed_pixels GL_APPLE_pixel_buffer GL_APPLE_rgb_422 GL_APPLE_row_bytes GL_APPLE_specular_vector GL_APPLE_texture_range GL_APPLE_transform_hint GL_APPLE_vertex_array_object GL_APPLE_vertex_array_range GL_APPLE_vertex_point_size GL_APPLE_vertex_program_evaluators GL_APPLE_ycbcr_422 GL_ATI_separate_stencil GL_ATI_texture_env_combine3 GL_ATI_texture_float GL_ATI_texture_mirror_once GL_IBM_rasterpos_clip GL_NV_blend_square GL_NV_conditional_render GL_NV_depth_clamp GL_NV_fog_distance GL_NV_light_max_exponent GL_NV_texgen_reflection GL_NV_texture_barrier GL_SGIS_generate_mipmap GL_SGIS_texture_edge_clamp GL_SGIS_texture_lod
Disabled Extensions	
Window system binding vendor	
Window system binding version	
Window system binding extensions	
Direct rendering	Yes
Reset notification strategy	0x0000
GPU process crash count	0
Compositor Information
Tile Update Mode	Zero-copy
Partial Raster	Disabled
GpuMemoryBuffers Status
ATC	Software only
ATCIA	Software only
DXT1	Software only
DXT5	Software only
ETC1	Software only
R_8	GPU_READ_CPU_READ_WRITE, GPU_READ_CPU_READ_WRITE_PERSISTENT
BGR_565	Software only
RGBA_4444	Software only
RGBX_8888	Software only
RGBA_8888	GPU_READ, SCANOUT
BGRX_8888	GPU_READ, SCANOUT
BGRA_8888	GPU_READ, SCANOUT, GPU_READ_CPU_READ_WRITE, GPU_READ_CPU_READ_WRITE_PERSISTENT
YVU_420	Software only
YUV_420_BIPLANAR	GPU_READ_CPU_READ_WRITE, GPU_READ_CPU_READ_WRITE_PERSISTENT
UYVY_422	GPU_READ_CPU_READ_WRITE, GPU_READ_CPU_READ_WRITE_PERSISTENT

Apologies, but I'm closing this as WontFix. If you search the Blink>WebGL category we are investigating more serious correctness issues at this point. Please file bugs ASAP if you reproduce problems like this, or more serious ones, on Canary.