## FlutterTimeline
Add a new class `FlutterTimeline` that's a drop-in replacement for `Timeline` from `dart:developer`. In addition to forwarding invocations of `startSync`, `finishSync`, `timeSync`, and `instantSync` to `dart:developer`, provides the following extra methods that make is easy to collect timings for code blocks on a frame-by-frame basis:
* `debugCollect()` - aggregates timings since the last reset, or since the app launched.
* `debugReset()` - forgets all data collected since the previous reset, or since the app launched. This allows clearing data from previous frames so timings can be attributed to the current frame.
* `now` - this was enhanced so that it works on the web by calling `window.performance.now` (in `Timeline` this is a noop in Dart web compilers).
* `collectionEnabled` - a field that controls whether `FlutterTimeline` stores timings in memory. By default this is disabled to avoid unexpected overhead (although the class is designed for minimal and predictable overhead). Specific benchmarks can enable collection to report to Skia Perf.
## Semantics benchmarks
Add `BenchMaterial3Semantics` that benchmarks the cost of semantics when constructing a screen full of Material 3 widgets from nothing. It is expected that semantics will have non-trivial cost in this case, but we should strive to keep it much lower than the rendering cost. This is the case already. This benchmark shows that the cost of semantics is <10%.
Add `BenchMaterial3ScrollSemantics` that benchmarks the cost of scrolling a previously constructed screen full of Material 3 widgets. The expectation should be that semantics will have trivial cost, since we're just shifting some widgets around. As of today, the numbers are not great, with semantics taking >50% of frame time, which is what prompted this PR in the first place. As we optimize this, we want to see this number improve.
* add asset manifest bin loading and asset manifest api
* use new api for image resolution
* remove upfront smc data casting
* fix typecasting issue
* remove unused import
* fix tests
* lints
* lints
* fix import
* revert image resolution changes
* Update image_resolution_test.dart
* Update decode_and_parse_asset_manifest.dart
* make targetDevicePixelRatio optional
* Update packages/flutter/lib/src/services/asset_manifest.dart
Co-authored-by: Jonah Williams <jonahwilliams@google.com>
* Update packages/flutter/lib/src/services/asset_manifest.dart
Co-authored-by: Jonah Williams <jonahwilliams@google.com>
* fix immutable not being imported
* return List in AssetManifest methods, fix annotation import
* simplify onError callback
* make AssetManifest methods abstract instead of throwing UnimplementedError
* simplify AssetVariant.key docstring
* tweak _AssetManifestBin docstring
* make AssetManifest and AssetVariant doc strings more specific
* use List.of instead of List.from for type-safety
* adjust import
* change _AssetManifestBin comment from doc comment to normal comment
* revert to callback function for onError in loadStructuredBinaryData
* add more to the docstring of AssetManifest.listAssets and AssetVariant.key
* add tests for CachingAssetBundle caching behavior
* add simple test to ensure loadStructuredBinaryData correctly calls load
* Update asset_manifest.dart
* update docstring for AssetManifest.getAssetVariants
* rename getAssetVariants, have it include main asset
* rename isMainAsset field of AssetMetadata to main
* (slightly) shorten name of describeAssetAndVariants
* rename describeAssetVariants back to getAssetVariants
* add tests for TestAssetBundle
* nits
* fix typo in docstring
* remove no longer necessary non-null asserts
* update gallery and google_fonts versions
---------
Co-authored-by: Jonah Williams <jonahwilliams@google.com>
* add asset manifest bin loading and asset manifest api
* use new api for image resolution
* remove upfront smc data casting
* fix typecasting issue
* remove unused import
* fix tests
* lints
* lints
* fix import
* revert image resolution changes
* Update image_resolution_test.dart
* Update decode_and_parse_asset_manifest.dart
* make targetDevicePixelRatio optional
* Update packages/flutter/lib/src/services/asset_manifest.dart
Co-authored-by: Jonah Williams <jonahwilliams@google.com>
* Update packages/flutter/lib/src/services/asset_manifest.dart
Co-authored-by: Jonah Williams <jonahwilliams@google.com>
* fix immutable not being imported
* return List in AssetManifest methods, fix annotation import
* simplify onError callback
* make AssetManifest methods abstract instead of throwing UnimplementedError
* simplify AssetVariant.key docstring
* tweak _AssetManifestBin docstring
* make AssetManifest and AssetVariant doc strings more specific
* use List.of instead of List.from for type-safety
* adjust import
* change _AssetManifestBin comment from doc comment to normal comment
* revert to callback function for onError in loadStructuredBinaryData
* add more to the docstring of AssetManifest.listAssets and AssetVariant.key
* add tests for CachingAssetBundle caching behavior
* add simple test to ensure loadStructuredBinaryData correctly calls load
* Update asset_manifest.dart
* update docstring for AssetManifest.getAssetVariants
* rename getAssetVariants, have it include main asset
* rename isMainAsset field of AssetMetadata to main
* (slightly) shorten name of describeAssetAndVariants
* rename describeAssetVariants back to getAssetVariants
* add tests for TestAssetBundle
* nits
* fix typo in docstring
* remove no longer necessary non-null asserts
Co-authored-by: Jonah Williams <jonahwilliams@google.com>
