I've found a few instances where Vulkan worked correctly but surface control did not. lets add a debugging flag we can ask folks to try to narrow down the issue.
1. Makes it possible to implement Impeller Vulkan -> Skia fallback.
2. Fixes https://github.com/flutter/flutter/issues/143871
3. Fixes https://github.com/flutter/flutter/issues/143873
4. Work towards https://github.com/flutter/flutter/issues/137798
Combines AndroidRenderingAPI + enable_impeller into a 4 values enum that describes all combinations of rendering behavior: ImpellerVulkan, ImpellerOpenGLES, SkiaOpenGLES, Software.
Updates the fallback behavior to happen in flutter_main. This allows us to change the value of Settings.enable_impeller to support an Impeller -> Skia fallback.
The Impeller context requires us to call Shutdown to ensure that all of its spawned worker threads are joined, ensuring that the raster thread retains the last reference. Without this, we may either destroy parts of the context to early, or attempt to join into a worker thread which will fail.
The new `BUILD.gn` files in the Engine tree can't go under
`build/secondary` because Skia still has its own, and they'd be selected
first. So, this PR puts the new `BUILD.gn` files under `flutter/skia`.
Noticed this while working on https://github.com/flutter/flutter/issues/124181
In Impeller right now, Android creates a context for each surface - but in Skia, Android creates one context and shares it across surfaces. For the multiple-engine scenario this matters. This also makes it possible for Android to provide the impeller::Context independently of surface creation.
This eliminates Vulkan support for Android. As of flutter/engine#27980
(684ad82) we are no longer running Android-Vulkan builds. This
eliminates the --enable-vulkan flag from tools/gn and any code that is
only reachable when that flag is enabled.
Note that after this patch, `shell_enable_vulkan` is always false,
however the //flutter/shell/gpu:gpu_surface_vulkan target and source
files remain since they are still used when `test_enable_vulkan` is
true, which is the case when `is_fuchsia` is true. Note that these files
are *not* built as part of a regular fuchsia build (see the
`shell_gpu_configuration` in //shell/platform/fuchsia/flutter/BUILD.gn),
but may be enabled once the Fuchsia embedder is migrated to the Embedder
API.
Also updates TODOs to dworsham, who is the committer who'll be
transitioning the Fuchsia embedder to the embedding API.
