[DRAFT][ios][platform_view]Use CAShapeLayer as the mask to avoid software rendering

[hellohuanlin]

This PR uses CAShapeLayer as the mask to avoid software rendering.

Running benchmark now, will post in comment.

See design doc: https://docs.google.com/document/d/1TqG_N4GK_qctuk73Gk3zOdAiILUrwMqxoCMgroK_AeA/edit?resourcekey=0-jUiidfzIS642ngG2w9vSUA&tab=t.0

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[hellohuanlin]

This is obviously still a draft since I haven't renamed mask_view_pool to mask_layer_pool etc.

[hellohuanlin]

@jonahwilliams @jmagman So this is still a draft PR, but wanna share the benchmark result first:

═════════════════════════╡ ••• A/B results so far ••• ╞═════════════════════════
Score	Average A (noise)	Average B (noise)	Speed-up
average_frame_build_time_millis		0.27 (4.64%)	
worst_frame_build_time_millis		0.79 (19.35%)	
90th_percentile_frame_build_time_millis		0.44 (6.86%)	
99th_percentile_frame_build_time_millis		0.63 (8.04%)	
average_frame_rasterizer_time_millis		3.59 (2.90%)	
worst_frame_rasterizer_time_millis		12.03 (18.04%)	
90th_percentile_frame_rasterizer_time_millis		6.16 (10.67%)	
99th_percentile_frame_rasterizer_time_millis		9.62 (15.11%)	
average_layer_cache_count		0.00 (0.00%)	
90th_percentile_layer_cache_count		0.00 (0.00%)	
99th_percentile_layer_cache_count		0.00 (0.00%)	
worst_layer_cache_count		0.00 (0.00%)	
average_layer_cache_memory		0.00 (0.00%)	
90th_percentile_layer_cache_memory		0.00 (0.00%)	
99th_percentile_layer_cache_memory		0.00 (0.00%)	
worst_layer_cache_memory		0.00 (0.00%)	
average_picture_cache_count		0.00 (0.00%)	
90th_percentile_picture_cache_count		0.00 (0.00%)	
99th_percentile_picture_cache_count		0.00 (0.00%)	
worst_picture_cache_count		0.00 (0.00%)	
average_picture_cache_memory		0.00 (0.00%)	
90th_percentile_picture_cache_memory		0.00 (0.00%)	
99th_percentile_picture_cache_memory		0.00 (0.00%)	
worst_picture_cache_memory		0.00 (0.00%)	
old_gen_gc_count		0.07 (538.52%)	
average_vsync_transitions_missed		0.58 (88.64%)	
90th_percentile_vsync_transitions_missed		0.60 (92.30%)	
99th_percentile_vsync_transitions_missed		0.70 (133.76%)	
average_frame_request_pending_latency		12736.34 (3.35%)	
90th_percentile_frame_request_pending_latency		15230.33 (2.32%)	
99th_percentile_frame_request_pending_latency		16407.67 (0.59%)	
average_cpu_usage		20.95 (13.81%)	
average_gpu_usage		7.19 (10.50%)	
average_memory_usage		175.05 (3.90%)	
90th_percentile_memory_usage		183.69 (5.62%)	
99th_percentile_memory_usage		189.17 (5.89%)	
total_ui_gc_time		1.43 (28.24%)	
30hz_frame_percentage		0.00 (0.00%)	
60hz_frame_percentage		100.00 (0.00%)	
80hz_frame_percentage		0.00 (0.00%)	
90hz_frame_percentage		0.00 (0.00%)	
120hz_frame_percentage		0.00 (0.00%)	
illegal_refresh_rate_frame_count		0.00 (0.00%)	
average_gpu_frame_time		1.07 (67.73%)	
90th_percentile_gpu_frame_time		0.00 (0.00%)	
99th_percentile_gpu_frame_time		39.58 (76.09%)	
worst_gpu_frame_time		54.17 (39.22%)	
average_gpu_memory_mb		0.00 (0.00%)	
90th_percentile_gpu_memory_mb		0.00 (0.00%)	
99th_percentile_gpu_memory_mb		0.00 (0.00%)	
worst_gpu_memory_mb		0.00 (0.00%)	

Observation
(I reused the benchmark of main branch here)

• avg: 3.67 -> 3.59 (down 2%)
• 90th: 6.13 -> 6.16 (up 0.5%)
• 99th: 10.43 -> 9.62 (down 7.8%)
• worst: 13.72 -> 12.03 (down 12.3%)

I think we should also ignore 90th/99th/worst due to large noise, and focus on the average frames, as discussed previously.

The result of this PR feels slightly better than clipsToBound, possibly because:

(1) it not only avoids software rendering, but also removes UIView; or
(2) just happen by chance

I think despite that the improvement is small (if any at all, due to noise), we should land it, let it run for a week or 2, and see a more accurate result

[hellohuanlin]

cross ref: #51661 (comment)

[jonahwilliams]

We should absolutely land this change, we know that software rasterization is slow - evne if there are other things going on on this benchmark. I would expect an improvement to 99%+ times and not average times, so we may need to run the benchmark on CI for a while to see an improvement there.

[hellohuanlin]

I am closing this in favor of #53072, because there are 2 improvements in this PR and I want to separate them:

(1) avoid software rendering (PR linked above);
(2) use CALayer instead of UIView (created new issue to track)

This allows us to (1) measure improvement separately for a better understanding; and also (2) we can land the software rendering PR sooner, since there are quite a lot of testing changes needed to complete this PR.