STR:

1. Enable gfx.webrender.all
2. Load http://outstream.com/
3. Wait for the phone, tablet, and laptop screenshots to load.
4. Mouse over the screenshots and watch them tilt.

RESULT:
The screenshot tilt effect is very slow in all browsers on my machine (Firefox, Chrome, and Edge) but it is at least smooth. With WebRender, the tilt effect is very laggy and jumpy.

Here is the graphics information from my about:support:

Application Basics

Name: Firefox
Version: 66.0a1
Build ID: 20190109163702
Update Channel: nightly
User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:66.0) Gecko/20100101 Firefox/66.0
OS: Windows_NT 10.0
Multiprocess Windows: 4/4 Unknown status
Web Content Processes: 10/8
Enterprise Policies: Inactive
Google Key: Found
Mozilla Location Service Key: Found
Safe Mode: false

Graphics

Features
Compositing: WebRender
asyncPanZoom: wheel input enabled; touch input enabled; scrollbar drag enabled; keyboard enabled; autoscroll enabled
webgl1WSIInfo: EGL_VENDOR: Google Inc. (adapter LUID: 000000000000ed1e) EGL_VERSION: 1.4 (ANGLE 2.1.0.790e8e6b4179) EGL_EXTENSIONS: EGL_EXT_create_context_robustness EGL_ANGLE_d3d_share_handle_client_buffer EGL_ANGLE_d3d_texture_client_buffer EGL_ANGLE_surface_d3d_texture_2d_share_handle EGL_ANGLE_query_surface_pointer EGL_ANGLE_window_fixed_size EGL_ANGLE_keyed_mutex EGL_ANGLE_surface_orientation EGL_ANGLE_direct_composition EGL_NV_post_sub_buffer EGL_KHR_create_context EGL_EXT_device_query EGL_KHR_image EGL_KHR_image_base EGL_KHR_gl_texture_2D_image EGL_KHR_gl_texture_cubemap_image EGL_KHR_gl_renderbuffer_image EGL_KHR_get_all_proc_addresses EGL_KHR_stream EGL_KHR_stream_consumer_gltexture EGL_NV_stream_consumer_gltexture_yuv EGL_ANGLE_flexible_surface_compatibility EGL_ANGLE_stream_producer_d3d_texture EGL_ANGLE_create_context_webgl_compatibility EGL_CHROMIUM_create_context_bind_generates_resource EGL_CHROMIUM_sync_control EGL_EXT_pixel_format_float EGL_KHR_surfaceless_context EGL_ANGLE_display_texture_share_group EGL_ANGLE_create_context_client_arrays EGL_ANGLE_program_cache_control EGL_ANGLE_robust_resource_initialization EGL_ANGLE_create_context_extensions_enabled EGL_MOZ_create_context_provoking_vertex_dont_care EGL_EXTENSIONS(nullptr): EGL_EXT_client_extensions EGL_EXT_platform_base EGL_EXT_platform_device EGL_ANGLE_platform_angle EGL_ANGLE_platform_angle_d3d EGL_ANGLE_device_creation EGL_ANGLE_device_creation_d3d11 EGL_ANGLE_experimental_present_path EGL_KHR_client_get_all_proc_addresses EGL_KHR_debug EGL_ANGLE_explicit_context
WebGL 1 Driver Renderer: Google Inc. -- ANGLE (Intel(R) UHD Graphics 630 Direct3D11 vs_5_0 ps_5_0)
WebGL 1 Driver Version: OpenGL ES 2.0 (ANGLE 2.1.0.790e8e6b4179)
WebGL 1 Driver Extensions: GL_ANGLE_client_arrays GL_ANGLE_depth_texture GL_ANGLE_explicit_context GL_ANGLE_explicit_context_gles1 GL_ANGLE_framebuffer_blit GL_ANGLE_framebuffer_multisample GL_ANGLE_instanced_arrays GL_ANGLE_lossy_etc_decode GL_ANGLE_pack_reverse_row_order GL_ANGLE_program_cache_control GL_ANGLE_request_extension GL_ANGLE_robust_client_memory GL_ANGLE_texture_compression_dxt3 GL_ANGLE_texture_compression_dxt5 GL_ANGLE_texture_usage GL_ANGLE_translated_shader_source GL_CHROMIUM_bind_generates_resource GL_CHROMIUM_bind_uniform_location GL_CHROMIUM_color_buffer_float_rgb GL_CHROMIUM_color_buffer_float_rgba GL_CHROMIUM_copy_compressed_texture GL_CHROMIUM_copy_texture GL_CHROMIUM_sync_query GL_EXT_blend_minmax GL_EXT_color_buffer_half_float GL_EXT_debug_marker GL_EXT_discard_framebuffer GL_EXT_disjoint_timer_query GL_EXT_draw_buffers GL_EXT_frag_depth GL_EXT_map_buffer_range GL_EXT_occlusion_query_boolean GL_EXT_read_format_bgra GL_EXT_robustness GL_EXT_sRGB GL_EXT_shader_texture_lod GL_EXT_texture_compression_dxt1 GL_EXT_texture_compression_s3tc_srgb GL_EXT_texture_filter_anisotropic GL_EXT_texture_format_BGRA8888 GL_EXT_texture_rg GL_EXT_texture_storage GL_EXT_unpack_subimage GL_KHR_debug GL_KHR_parallel_shader_compile GL_KHR_robust_buffer_access_behavior GL_NV_EGL_stream_consumer_external GL_NV_fence GL_NV_pack_subimage GL_NV_pixel_buffer_object GL_OES_EGL_image GL_OES_EGL_image_external GL_OES_compressed_ETC1_RGB8_texture GL_OES_depth32 GL_OES_element_index_uint GL_OES_get_program_binary GL_OES_mapbuffer GL_OES_packed_depth_stencil GL_OES_rgb8_rgba8 GL_OES_standard_derivatives GL_OES_surfaceless_context GL_OES_texture_float GL_OES_texture_float_linear GL_OES_texture_half_float GL_OES_texture_half_float_linear GL_OES_texture_npot GL_OES_vertex_array_object OES_compressed_EAC_R11_signed_texture OES_compressed_EAC_R11_unsigned_texture OES_compressed_EAC_RG11_signed_texture OES_compressed_EAC_RG11_unsigned_texture OES_compressed_ETC2_RGB8_texture OES_compressed_ETC2_RGBA8_texture OES_compressed_ETC2_punchthroughA_RGBA8_texture OES_compressed_ETC2_punchthroughA_sRGB8_alpha_texture OES_compressed_ETC2_sRGB8_alpha8_texture OES_compressed_ETC2_sRGB8_texture
WebGL 1 Extensions: ANGLE_instanced_arrays EXT_blend_minmax EXT_color_buffer_half_float EXT_frag_depth EXT_sRGB EXT_shader_texture_lod EXT_texture_filter_anisotropic EXT_disjoint_timer_query OES_element_index_uint OES_standard_derivatives OES_texture_float OES_texture_float_linear OES_texture_half_float OES_texture_half_float_linear OES_vertex_array_object WEBGL_color_buffer_float WEBGL_compressed_texture_s3tc WEBGL_compressed_texture_s3tc_srgb WEBGL_debug_renderer_info WEBGL_debug_shaders WEBGL_depth_texture WEBGL_draw_buffers WEBGL_lose_context
WebGL 2 Driver WSI Info: EGL_VENDOR: Google Inc. (adapter LUID: 000000000000ed1e) EGL_VERSION: 1.4 (ANGLE 2.1.0.790e8e6b4179) EGL_EXTENSIONS: EGL_EXT_create_context_robustness EGL_ANGLE_d3d_share_handle_client_buffer EGL_ANGLE_d3d_texture_client_buffer EGL_ANGLE_surface_d3d_texture_2d_share_handle EGL_ANGLE_query_surface_pointer EGL_ANGLE_window_fixed_size EGL_ANGLE_keyed_mutex EGL_ANGLE_surface_orientation EGL_ANGLE_direct_composition EGL_NV_post_sub_buffer EGL_KHR_create_context EGL_EXT_device_query EGL_KHR_image EGL_KHR_image_base EGL_KHR_gl_texture_2D_image EGL_KHR_gl_texture_cubemap_image EGL_KHR_gl_renderbuffer_image EGL_KHR_get_all_proc_addresses EGL_KHR_stream EGL_KHR_stream_consumer_gltexture EGL_NV_stream_consumer_gltexture_yuv EGL_ANGLE_flexible_surface_compatibility EGL_ANGLE_stream_producer_d3d_texture EGL_ANGLE_create_context_webgl_compatibility EGL_CHROMIUM_create_context_bind_generates_resource EGL_CHROMIUM_sync_control EGL_EXT_pixel_format_float EGL_KHR_surfaceless_context EGL_ANGLE_display_texture_share_group EGL_ANGLE_create_context_client_arrays EGL_ANGLE_program_cache_control EGL_ANGLE_robust_resource_initialization EGL_ANGLE_create_context_extensions_enabled EGL_MOZ_create_context_provoking_vertex_dont_care EGL_EXTENSIONS(nullptr): EGL_EXT_client_extensions EGL_EXT_platform_base EGL_EXT_platform_device EGL_ANGLE_platform_angle EGL_ANGLE_platform_angle_d3d EGL_ANGLE_device_creation EGL_ANGLE_device_creation_d3d11 EGL_ANGLE_experimental_present_path EGL_KHR_client_get_all_proc_addresses EGL_KHR_debug EGL_ANGLE_explicit_context
WebGL 2 Driver Renderer: Google Inc. -- ANGLE (Intel(R) UHD Graphics 630 Direct3D11 vs_5_0 ps_5_0)
WebGL 2 Driver Version: OpenGL ES 3.0 (ANGLE 2.1.0.790e8e6b4179)
WebGL 2 Driver Extensions: GL_ANGLE_client_arrays GL_ANGLE_depth_texture GL_ANGLE_explicit_context GL_ANGLE_explicit_context_gles1 GL_ANGLE_framebuffer_blit GL_ANGLE_framebuffer_multisample GL_ANGLE_instanced_arrays GL_ANGLE_lossy_etc_decode GL_ANGLE_multiview GL_ANGLE_pack_reverse_row_order GL_ANGLE_program_cache_control GL_ANGLE_request_extension GL_ANGLE_robust_client_memory GL_ANGLE_texture_compression_dxt3 GL_ANGLE_texture_compression_dxt5 GL_ANGLE_texture_usage GL_ANGLE_translated_shader_source GL_CHROMIUM_bind_generates_resource GL_CHROMIUM_bind_uniform_location GL_CHROMIUM_color_buffer_float_rgb GL_CHROMIUM_color_buffer_float_rgba GL_CHROMIUM_copy_compressed_texture GL_CHROMIUM_copy_texture GL_CHROMIUM_sync_query GL_EXT_blend_minmax GL_EXT_color_buffer_float GL_EXT_color_buffer_half_float GL_EXT_debug_marker GL_EXT_discard_framebuffer GL_EXT_disjoint_timer_query GL_EXT_draw_buffers GL_EXT_frag_depth GL_EXT_map_buffer_range GL_EXT_occlusion_query_boolean GL_EXT_read_format_bgra GL_EXT_robustness GL_EXT_sRGB GL_EXT_shader_texture_lod GL_EXT_texture_compression_dxt1 GL_EXT_texture_compression_s3tc_srgb GL_EXT_texture_filter_anisotropic GL_EXT_texture_format_BGRA8888 GL_EXT_texture_norm16 GL_EXT_texture_rg GL_EXT_texture_storage GL_EXT_unpack_subimage GL_KHR_debug GL_KHR_parallel_shader_compile GL_KHR_robust_buffer_access_behavior GL_NV_EGL_stream_consumer_external GL_NV_fence GL_NV_pack_subimage GL_NV_pixel_buffer_object GL_OES_EGL_image GL_OES_EGL_image_external GL_OES_EGL_image_external_essl3 GL_OES_compressed_ETC1_RGB8_texture GL_OES_depth32 GL_OES_element_index_uint GL_OES_get_program_binary GL_OES_mapbuffer GL_OES_packed_depth_stencil GL_OES_rgb8_rgba8 GL_OES_standard_derivatives GL_OES_surfaceless_context GL_OES_texture_float GL_OES_texture_float_linear GL_OES_texture_half_float GL_OES_texture_half_float_linear GL_OES_texture_npot GL_OES_vertex_array_object OES_compressed_EAC_R11_signed_texture OES_compressed_EAC_R11_unsigned_texture OES_compressed_EAC_RG11_signed_texture OES_compressed_EAC_RG11_unsigned_texture OES_compressed_ETC2_RGB8_texture OES_compressed_ETC2_RGBA8_texture OES_compressed_ETC2_punchthroughA_RGBA8_texture OES_compressed_ETC2_punchthroughA_sRGB8_alpha_texture OES_compressed_ETC2_sRGB8_alpha8_texture OES_compressed_ETC2_sRGB8_texture
WebGL 2 Extensions: EXT_color_buffer_float EXT_texture_filter_anisotropic EXT_disjoint_timer_query OES_texture_float_linear WEBGL_compressed_texture_s3tc WEBGL_compressed_texture_s3tc_srgb WEBGL_debug_renderer_info WEBGL_debug_shaders WEBGL_lose_context
Direct2D: true
Uses Tiling (Content): true
Off Main Thread Painting Enabled: true
Off Main Thread Painting Worker Count: 4
Target Frame Rate: 60
DirectWrite: true (10.0.17763.168)
GPU #1
Active: Yes
Description: Intel(R) UHD Graphics 630
Vendor ID: 0x8086
Device ID: 0x3e9b
Driver Version: 24.20.100.6287
Driver Date: 8-15-2018
Drivers: igdumdim64 igd10iumd64 igd10iumd64 igd12umd64 igdumdim32 igd10iumd32 igd10iumd32 igd12umd32
Subsys ID: 087c1028
RAM: Unknown
GPU #2
Active: No
Description: NVIDIA GeForce GTX 1050 Ti with Max-Q Design
Vendor ID: 0x10de
Device ID: 0x1c8c
Driver Version: 24.21.13.9793
Driver Date: 5-22-2018
Drivers: C:\Windows\System32\DriverStore\FileRepository\nvdm.inf_amd64_786f30519164c09a\nvldumdx.dll,C:\Windows\System32\DriverStore\FileRepository\nvdm.inf_amd64_786f30519164c09a\nvldumdx.dll,C:\Windows\System32\DriverStore\FileRepository\nvdm.inf_amd64_786f30519164c09a\nvldumdx.dll,C:\Windows\System32\DriverStore\FileRepository\nvdm.inf_amd64_786f30519164c09a\nvldumdx.dll C:\Windows\System32\DriverStore\FileRepository\nvdm.inf_amd64_786f30519164c09a\nvldumd.dll,C:\Windows\System32\DriverStore\FileRepository\nvdm.inf_amd64_786f30519164c09a\nvldumd.dll,C:\Windows\System32\DriverStore\FileRepository\nvdm.inf_amd64_786f30519164c09a\nvldumd.dll,C:\Windows\System32\DriverStore\FileRepository\nvdm.inf_amd64_786f30519164c09a\nvldumd.dll
Subsys ID: 087c1028
RAM: 4096
Diagnostics
AzureCanvasAccelerated: 0
AzureCanvasBackend: direct2d 1.1
AzureCanvasBackend (UI Process): skia
AzureContentBackend: skia
AzureContentBackend (UI Process): skia
AzureFallbackCanvasBackend (UI Process): cairo
Slow Frame #01: Frame 67(https://blog.chromium.org/2019/01/building-better-world-wide-web.html) CONTENT_FRAME_TIME 4274090 - Transaction start 0.000000, main-thread time 5.426000, full paint time 7.247100, Skipped composites 0, Composite start 22.036700, Resource upload time 0.000600, GPU cache upload time 0.178300, Render time 16.667100, Composite time 33.296900
Slow Frame #02: Frame 98(https://github.com/mozilla-mobile/reference-browser/issues) CONTENT_FRAME_TIME 205967 - Transaction start 0.000000, main-thread time 12.079100, full paint time 18.033000, Skipped composites 0, Composite start 35.410900, Resource upload time 0.161800, GPU cache upload time 0.160000, Render time 3.669600, Composite time 5.708100
Slow Frame #03: Frame 6(https://github.com/mozilla-mobile/reference-browser/issues/392) CONTENT_FRAME_TIME 159987 - Transaction start 0.000000, main-thread time 15.664300, full paint time 23.963000, Skipped composites 0, Composite start 24.799100, Resource upload time 0.000400, GPU cache upload time 0.133600, Render time 4.331300, Composite time 9.549200
Slow Frame #04: Frame 70(https://blog.chromium.org/2019/01/building-better-world-wide-web.html) CONTENT_FRAME_TIME 127636 - Transaction start 0.000000, main-thread time 2.968700, full paint time 4.384300, Skipped composites 0, Composite start 11.444400, Resource upload time 0.015500, GPU cache upload time 0.157000, Render time 2.009400, Composite time 5.314400
Slow Frame #05: Frame 96(https://github.com/mozilla-mobile/reference-browser/issues) CONTENT_FRAME_TIME 96528 - Transaction start 0.000000, main-thread time 5.521900, full paint time 8.526600, Skipped composites 0, Composite start 12.509100, Resource upload time 0.237100, GPU cache upload time 0.099900, Render time 2.319800, Composite time 3.930600
Slow Frame #06: Frame 1057(https://github.com/mozilla-mobile/reference-browser/issues/392) CONTENT_FRAME_TIME 95245 - Transaction start 0.000000, main-thread time 17.492600, full paint time 26.658200, Skipped composites 0, Composite start 31.414200, Resource upload time 0.452900, GPU cache upload time 0.139400, Render time 2.909000, Composite time 5.694800
Slow Frame #07: Frame 39(https://bugzilla.mozilla.org/show_bug.cgi?id=1420680#c66) CONTENT_FRAME_TIME 82528 - Transaction start 0.000000, main-thread time 14.878900, full paint time 17.654800, Skipped composites 0, Composite start 29.696200, Resource upload time 0.000300, GPU cache upload time 0.096800, Render time 1.140700, Composite time 3.122700
Slow Frame #08: Frame 88(https://blog.chromium.org/2019/01/building-better-world-wide-web.html) CONTENT_FRAME_TIME 67318 - Transaction start 0.000000, main-thread time 2.843000, full paint time 3.816900, Skipped composites 0, Composite start 3.904400, Resource upload time 0.000300, GPU cache upload time 0.068000, Render time 1.460500, Composite time 2.358900
Slow Frame #09: Frame 115(https://docs.google.com/document/d/1e-wh4Ubup8w9E7jrItIfELm90diYYMv4He4ybq2B0S4/edit) CONTENT_FRAME_TIME 63645 - Transaction start 0.000000, main-thread time 3.906400, full paint time 5.554300, Skipped composites 0, Composite start 5.947800, Resource upload time 0.000300, GPU cache upload time 0.123700, Render time 2.642500, Composite time 4.271300
Slow Frame #10: Frame 65(https://blog.chromium.org/2019/01/building-better-world-wide-web.html) CONTENT_FRAME_TIME 52352 - Transaction start 0.000000, main-thread time 6.359300, full paint time 12.346500, Skipped composites 0, Composite start 18.980000, Resource upload time 0.000600, GPU cache upload time 0.104500, Render time 3.584300, Composite time 6.922800
GPUProcessPid: 17004
GPUProcess: Terminate GPU Process
Device Reset: Trigger Device Reset
Decision Log
WEBRENDER:
opt-in by default: WebRender is an opt-in feature
available by user: Force enabled by pref
WEBRENDER_QUALIFIED:
blocked by env: Has battery

This is spending a lot of time in clipping maybe the same problem as bug 1504590

A few data points for non-windows platforms:

• This animation is pretty terrible for me on Linux, with or without WebRender. It's nice in Chrome. (But smaug says it's nice on his Linux Nightly, so your mileage may vary.)
• It's super smooth in Jean's Mac, in Firefox Nightly (only tested in default configuration, without webrender)

Frame building times are dominated by glyph rasterization and texture cache bookkeeping. All of the text in the moving planes is constently re-rasterized.
Other than that GPU times are pretty bad. Lots of it is attributed to target init, images and glyphs.

That domain is parked now. I tried a few versions of the old page from archive.org and it seems to run well now.