This PR limits the framework generated semantic node IDs to be smaller than 2^16, this allows to safely generate semantic node in the engine with IDs >= 2^16 avoiding ID collision (which is done in flutter/engine#8250).

https://github.com/flutter/engine/compare/af64f725f6c7...0d83a2ecd1bb

git log af64f725f6c74f5d1287a8be8511691119354088..0d83a2ecd1bb78f8e1f0ed9719ff3751cdfdd064 --no-merges --oneline
0d83a2ecd Roll src/third_party/skia 15dc59e65cfa..c5ee499f2c59 (2 commits) (flutter/engine#8298)
42d062f95 [fuchsia] Add missing trace macros (flutter/engine#8297)

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https://github.com/flutter/engine/compare/dd6be2fd8371...af64f725f6c7

git log dd6be2fd83710de8392fb554927a5d495684a13e..af64f725f6c74f5d1287a8be8511691119354088 --no-merges --oneline
af64f725f Fixing links between higher and lower classes. (flutter/engine#8295)
22ee8ee08 Migrate existing embedder unit tests to use the fixture. (flutter/engine#8296)
345ae7d37 Delegate a11y events and action to/from embedded Android platform views. (flutter/engine#8250)

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We can remove the hack because https://github.com/flutter/engine/pull/8183
has been rolled into the framework.

https://github.com/flutter/engine/compare/3a445cec8a51...dd6be2fd8371

git log 3a445cec8a51056e5903c12659b6fc97138e57db..dd6be2fd83710de8392fb554927a5d495684a13e --no-merges --oneline
dd6be2fd8 Roll src/third_party/skia 42197c0bc68e..15dc59e65cfa (19 commits) (flutter/engine#8294)
d6ead18f4 Make it easy to write embedder unit tests by creating a fixture and config builder. (flutter/engine#8276)

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https://github.com/flutter/engine/compare/dcc72c7176bc...3a445cec8a51

git log dcc72c7176bcaa9fc9fa3798542f764ca6fe4ebc..3a445cec8a51056e5903c12659b6fc97138e57db --no-merges --oneline
3a445cec8 Roll src/third_party/skia cd54466473fe..42197c0bc68e (10 commits) (flutter/engine#8292)
fcc63e7d0 Roll src/third_party/skia 2e2fa9e3a06b..cd54466473fe (2 commits) (flutter/engine#8291)
1b1209881 Roll src/third_party/skia c9f746cfb9f4..2e2fa9e3a06b (1 commits) (flutter/engine#8290)
b5813917f Roll src/third_party/skia e9a53fe3526a..c9f746cfb9f4 (1 commits) (flutter/engine#8288)

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The @flutterio account now just directs people to @FlutterDev:

https://twitter.com/flutterio

dcc72c717 Roll src/third_party/skia d79c95e8bcf2..e9a53fe3526a (1 commits) (flutter/engine#8287) (#29874)


https://github.com/flutter/engine/compare/d2bba21af27a...dcc72c7176bc

git log d2bba21af27a8d3f30c66aa014f324c786f3fb4e..dcc72c7176bcaa9fc9fa3798542f764ca6fe4ebc --no-merges --oneline
dcc72c717 Roll src/third_party/skia d79c95e8bcf2..e9a53fe3526a (1 commits) (flutter/engine#8287)

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https://github.com/flutter/engine/compare/9f878fcb3ecd...d2bba21af27a

git log 9f878fcb3ecdcc2c6ba0c6d958282c176f008183..d2bba21af27a8d3f30c66aa014f324c786f3fb4e --no-merges --oneline
d2bba21af Roll src/third_party/skia ab4c138c0ef3..d79c95e8bcf2 (2 commits) (flutter/engine#8286)
cee2bd732 Roll src/third_party/skia 97d957d1db65..ab4c138c0ef3 (3 commits) (flutter/engine#8285)
ef3cbe8ac Roll src/third_party/skia 4c0b5c4b79dd..97d957d1db65 (1 commits) (flutter/engine#8284)
bd4f6d726 Roll src/third_party/skia b1dbbc8509c6..4c0b5c4b79dd (2 commits) (flutter/engine#8283)
8d23b21d1 Roll src/third_party/skia 61bd91237778..b1dbbc8509c6 (2 commits) (flutter/engine#8282)
61838cab6 Roll src/third_party/skia ec1c6fdfdd11..61bd91237778 (1 commits) (flutter/engine#8280)

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9f878fcb3 Roll src/third_party/skia e86cc5039026..ec1c6fdfdd11 (1 commits) (flutter/engine#8279) (#29836)


https://github.com/flutter/engine/compare/62c88d690272...9f878fcb3ecd

git log 62c88d690272f0b78047758bb9d8ffa8bbb870cc..9f878fcb3ecdcc2c6ba0c6d958282c176f008183 --no-merges --oneline
9f878fcb3 Roll src/third_party/skia e86cc5039026..ec1c6fdfdd11 (1 commits) (flutter/engine#8279)

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62c88d690 Roll src/third_party/skia 33332f1e100c..e86cc5039026 (1 commits) (flutter/engine#8278) (#29832)


https://github.com/flutter/engine/compare/f8e3a40f9ba7...62c88d690272

git log f8e3a40f9ba701120724b5d6e8ff790d50f18083..62c88d690272f0b78047758bb9d8ffa8bbb870cc --no-merges --oneline
62c88d690 Roll src/third_party/skia 33332f1e100c..e86cc5039026 (1 commits) (flutter/engine#8278)

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https://github.com/flutter/engine/compare/5f8ae420c1ac...f8e3a40f9ba7

git log 5f8ae420c1ac61bbbb26e61251d129c879fc788d..f8e3a40f9ba701120724b5d6e8ff790d50f18083 --no-merges --oneline
f8e3a40f9 Roll buildroot to 9c7b023ff266ee58b00fe60326fa1db910a087f3 (flutter/engine#8277)
c12696cc5 Roll src/third_party/skia f9264bac4e99..33332f1e100c (27 commits) (flutter/engine#8275)

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* Detect and cleanup leaky processes
* Add flaky tests for detecting leaked processes

This reverts commit e38be671.

https://github.com/flutter/engine/compare/d4d4883216fd...b68f7e72aa71

git log d4d4883216fd1c1dfc17d41418a960c002cfff57..b68f7e72aa71eb75969bd674d78a5b40ee5ed89f --no-merges --oneline
b68f7e72a Allow specifying an alternate Mac host SDK. (flutter/engine#8249)
3df694300 Roll src/third_party/dart cabaa78cc5..ba0147ac07 (3 commits) (flutter/engine#8248)
69c4d82f5 Roll src/third_party/skia d6ab77a2e20f..19fb3971bca5 (17 commits) (flutter/engine#8245)
06635d38a Mirror Android platform views a11y tree in the Flutter a11y tree. (flutter/engine#8237)
28433c513 FlutterJNI no longer asserts it is attached when dispatching platform messages and instead fizzles with a warning if not attached. Not sure what root cause of issue is, but this is necessary to avoid crashes. (flutter/engine#8246)
1addfb596 Roll src/third_party/dart 5e9df35a57..cabaa78cc5 (36 commits) (flutter/engine#8244)
13e3b7101 Roll src/third_party/skia a695da930510..d6ab77a2e20f (11 commits) (flutter/engine#8243)

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This results in running Flutter Gallery with one less thread (platform
and gpu threads are the the same).

This is very likely to cause a regression in the iOS Gallery benchmarks.
I'm mainly interested in landing this to see how much the benchmarks
regress, and it's likely that we will revert it shortly after landing.