Fixes https://github.com/flutter/flutter/issues/128412
Adds
- `DlRegion DlRegion::MakeUnion(const Region &, const DlRegion &)`
- `DlRegion DlRegion::MakeIntersection(const Region &, const DlRegion
&)`
- `bool DlRegion::intersects(const DlRegion &)`
- `bool DlRegion::intersects(const SkIRect &)`
Instead of per span line vector all spans are stored in continuous
buffer.
Complete benchmarks:
```
-----------------------------------------------------------------------------------------------
Benchmark Time CPU Iterations
-----------------------------------------------------------------------------------------------
BM_DlRegion_IntersectsSingleRect/Tiny 2688 ns 2687 ns 258580
BM_SkRegion_IntersectsSingleRect/Tiny 85889 ns 85877 ns 8092
BM_DlRegion_IntersectsSingleRect/Small 4814 ns 4813 ns 142874
BM_SkRegion_IntersectsSingleRect/Small 101102 ns 101102 ns 6833
BM_DlRegion_IntersectsSingleRect/Medium 2329 ns 2329 ns 302911
BM_SkRegion_IntersectsSingleRect/Medium 60436 ns 60183 ns 11156
BM_DlRegion_IntersectsSingleRect/Large 1243 ns 1243 ns 565209
BM_SkRegion_IntersectsSingleRect/Large 2813 ns 2813 ns 252187
BM_DlRegion_IntersectsRegion/Tiny 38.9 ns 38.9 ns 17913855
BM_SkRegion_IntersectsRegion/Tiny 203 ns 203 ns 3480855
BM_DlRegion_IntersectsRegion/Small 306 ns 306 ns 2295413
BM_SkRegion_IntersectsRegion/Small 1057 ns 1057 ns 660826
BM_DlRegion_IntersectsRegion/Medium 8.83 ns 8.83 ns 79128233
BM_SkRegion_IntersectsRegion/Medium 43.3 ns 43.3 ns 16076912
BM_DlRegion_IntersectsRegion/Large 6.96 ns 6.96 ns 101646676
BM_SkRegion_IntersectsRegion/Large 31.8 ns 31.8 ns 22121517
BM_DlRegion_IntersectsRegion/TinyAsymmetric 54.2 ns 54.2 ns 12890870
BM_SkRegion_IntersectsRegion/TinyAsymmetric 4575 ns 4574 ns 155368
BM_DlRegion_IntersectsRegion/SmallAsymmetric 190 ns 189 ns 3748547
BM_SkRegion_IntersectsRegion/SmallAsymmetric 6157 ns 6157 ns 114403
BM_DlRegion_IntersectsRegion/MediumAsymmetric 20.9 ns 20.9 ns 33523941
BM_SkRegion_IntersectsRegion/MediumAsymmetric 3247 ns 3247 ns 214694
BM_DlRegion_IntersectsRegion/LargeAsymmetric 8.97 ns 8.97 ns 76827676
BM_SkRegion_IntersectsRegion/LargeAsymmetric 154 ns 154 ns 4757924
BM_DlRegion_Operation/Union_Tiny 26.3 us 26.3 us 24534
BM_SkRegion_Operation/Union_Tiny 37.9 us 37.9 us 17973
BM_DlRegion_Operation/Union_Small 64.4 us 64.4 us 10657
BM_SkRegion_Operation/Union_Small 105 us 105 us 6278
BM_DlRegion_Operation/Union_Medium 22.0 us 22.0 us 31631
BM_SkRegion_Operation/Union_Medium 64.8 us 64.8 us 10744
BM_DlRegion_Operation/Union_Large 1.00 us 1.00 us 697406
BM_SkRegion_Operation/Union_Large 1.29 us 1.29 us 547089
BM_DlRegion_Operation/Union_TinyAsymmetric 10.3 us 10.3 us 68647
BM_SkRegion_Operation/Union_TinyAsymmetric 20.6 us 20.6 us 33282
BM_DlRegion_Operation/Union_SmallAsymmetric 14.0 us 14.0 us 49944
BM_SkRegion_Operation/Union_SmallAsymmetric 34.4 us 34.4 us 19618
BM_DlRegion_Operation/Union_MediumAsymmetric 5.24 us 5.24 us 134097
BM_SkRegion_Operation/Union_MediumAsymmetric 12.7 us 12.7 us 55069
BM_DlRegion_Operation/Union_LargeAsymmetric 0.376 us 0.376 us 1808589
BM_SkRegion_Operation/Union_LargeAsymmetric 0.533 us 0.532 us 1283674
BM_DlRegion_Operation/Intersection_Tiny 8.13 us 8.13 us 87199
BM_SkRegion_Operation/Intersection_Tiny 31.8 us 31.8 us 21864
BM_DlRegion_Operation/Intersection_Small 55.9 us 55.9 us 11888
BM_SkRegion_Operation/Intersection_Small 98.4 us 98.3 us 6963
BM_DlRegion_Operation/Intersection_Medium 40.0 us 40.0 us 17667
BM_SkRegion_Operation/Intersection_Medium 69.8 us 69.8 us 9910
BM_DlRegion_Operation/Intersection_Large 1.06 us 1.06 us 650957
BM_SkRegion_Operation/Intersection_Large 1.26 us 1.26 us 559624
BM_DlRegion_Operation/Intersection_TinyAsymmetric 2.62 us 2.62 us 264565
BM_SkRegion_Operation/Intersection_TinyAsymmetric 15.3 us 15.3 us 45528
BM_DlRegion_Operation/Intersection_SmallAsymmetric 7.15 us 7.15 us 93482
BM_SkRegion_Operation/Intersection_SmallAsymmetric 27.5 us 27.5 us 24450
BM_DlRegion_Operation/Intersection_MediumAsymmetric 2.95 us 2.95 us 235133
BM_SkRegion_Operation/Intersection_MediumAsymmetric 10.5 us 10.5 us 65925
BM_DlRegion_Operation/Intersection_LargeAsymmetric 0.165 us 0.165 us 4016433
BM_SkRegion_Operation/Intersection_LargeAsymmetric 0.409 us 0.409 us 1719716
BM_DlRegion_Operation/Intersection_SingleRect_Tiny 0.105 us 0.105 us 7403099
BM_SkRegion_Operation/Intersection_SingleRect_Tiny 10.8 us 10.8 us 64185
BM_DlRegion_Operation/Intersection_SingleRect_Small 0.410 us 0.410 us 1724524
BM_SkRegion_Operation/Intersection_SingleRect_Small 16.2 us 16.2 us 43707
BM_DlRegion_Operation/Intersection_SingleRect_Medium 0.458 us 0.458 us 1540049
BM_SkRegion_Operation/Intersection_SingleRect_Medium 7.54 us 7.54 us 93407
BM_DlRegion_Operation/Intersection_SingleRect_Large 0.175 us 0.175 us 3984926
BM_SkRegion_Operation/Intersection_SingleRect_Large 0.351 us 0.351 us 1931946
BM_DlRegion_FromRects/Tiny 154 us 154 us 4383
BM_SkRegion_FromRects/Tiny 69429 us 69419 us 10
BM_DlRegion_FromRects/Small 369 us 369 us 1932
BM_SkRegion_FromRects/Small 117584 us 117578 us 6
BM_DlRegion_FromRects/Medium 475 us 475 us 1477
BM_SkRegion_FromRects/Medium 21611 us 21610 us 33
BM_DlRegion_FromRects/Large 1329 us 1329 us 533
BM_SkRegion_FromRects/Large 1409 us 1409 us 501
BM_DlRegion_GetRects/Tiny 39.2 us 39.2 us 18030
BM_SkRegion_GetRects/Tiny 84.2 us 84.2 us 9971
BM_DlRegion_GetRects/Small 88.9 us 88.9 us 7873
BM_SkRegion_GetRects/Small 212 us 212 us 3598
BM_DlRegion_GetRects/Medium 0.845 us 0.813 us 881224
BM_SkRegion_GetRects/Medium 3.10 us 3.09 us 223483
BM_DlRegion_GetRects/Large 0.120 us 0.120 us 5954761
BM_SkRegion_GetRects/Large 0.337 us 0.336 us 2068656
```
## Pre-launch Checklist
- [X] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [X] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [X] I read and followed the [Flutter Style Guide] and the [C++,
Objective-C, Java style guides].
- [X] I listed at least one issue that this PR fixes in the description
above.
- [X] I added new tests to check the change I am making or feature I am
adding, or Hixie said the PR is test-exempt. See [testing the engine]
for instructions on writing and running engine tests.
- [X] I updated/added relevant documentation (doc comments with `///`).
- [X] I signed the [CLA].
- [X] All existing and new tests are passing.
If you need help, consider asking for advice on the #hackers-new channel
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