Fixes https://github.com/flutter/flutter/issues/127090.
https://github.com/flutter/flutter/pull/122505 did a few things to speed up the first asset load that a flutter app performs. One of those things was to not include the main asset in its own list of variants in the asset manifest. The idea was that we know that the main asset always exists, so including it in its list of variants is a waste of storage space and loading time (even if the cost was tiny).
However, the assumption that the main asset always exists is wrong. From [Declaring resolution-aware image assets](https://docs.flutter.dev/ui/assets-and-images#resolution-aware), which predates https://github.com/flutter/flutter/pull/122505:
> Each entry in the asset section of the pubspec.yaml should correspond to a real file, with the exception of the main asset entry. If the main asset entry doesnât correspond to a real file, then the asset with the lowest resolution is used as the fallback for devices with device pixel ratios below that resolution. The entry should still be included in the pubspec.yaml manifest, however.
For example, it's valid to declare `assets/image.png` as an asset even if only `assets/3x/image.png` exists on disk.
This fix restores older behavior of including a main asset as a variant of itself in the manifest if it exists.
This fix also includes a non-user-visible behavior change:
* `"dpr"` is no longer a required field in the asset manifest's underlying structure. For the main asset entry, we do not include `"dpr"`. It makes less sense for the tool to decide what the default target dpr for an image should be. This should be left to the framework.
Instead of loading the use-material-design asset data from a yaml file in the repo, leave it in dart code and simplify. Remove some of the globals, but not enough to update to testWithoutContext
Fixes#45075Fixes#57210
If an asset was included directly from the project root directory, then the same asset when copied to various output or ephemeral directories would also be picked up as an asset variant. This could cause assets to be recursively copied into asset/build/ephemeral directories, as each time it would run it would pick up all of the previous "variants".
The solution is to include project ephemeral directories, in addition to the build directory.
The global packages path could cause tests to fail when it would be overriden to unexpected (in test setup) values. Remove most usage and make it a configuration on buildInfo, along with most other build information. Cleanup the asset builder to require the .packages path and the resident runners to no longer require it, since they already have the information in build_info.
It needs to stick around for the fuchsia deps we do not control.
Filled #60232 for remaining work.
If a dependency specified uses-material-design: true and the main pubspec specifies uses-material-design: false, then the MaterialIcons font would be included in the font manifest, but not in the AssetManifest or final bundle. Remove it from the FontManifest if this occurs
Work towards #16723
This is only safe to land after #58131 lands in google3. Only build NOTICES in asset manfiest, and load either LICENSE or NOTICES from pubspec dependencies.
