[skia-sync] Update skia to milestone 151

[mattleibow]

Automated Skia milestone bump from m150 to m151.

Companion skia PR: mono/skia#274

Update Skia to milestone 151 (m150 → m151)

Summary

Bumps the bundled Skia fork from chrome/m150 to chrome/m151 and SkiaSharp from 4.150.0 to 4.151.0.

• Submodule: externals/skia advances from b16789ec352c… to a2147f95b91d… (parent commit hash recorded in cgmanifest.json).
• Submodule branch: skia-sync/m151 (327 upstream commits merged + 1 C API fix).
• Milestone: 150 → 151. soname: libSkiaSharp.so.150.0.0 → libSkiaSharp.so.151.0.0. NuGet: 4.150.0 → 4.151.0.
• SK_C_INCREMENT: unchanged at 0 (milestone change resets the increment).
• HarfBuzz soname: unchanged (HarfBuzz was not bumped in this sync).

Breaking change analysis

Area	Status
C API surface (include/c/*.h, src/c/*.cpp)	No additions, no removals, no signature changes — verified by regenerate-bindings.ps1 producing zero diffs in SkiaApi.generated.cs (or any other generated binding).
C++ Skia upstream	include/private/base/* headers flattened to include/private/* (the private/base/ subdirectory is gone in m151). Only one of our C API files referenced this path; fix applied in the submodule.
ABI	Stable for managed callers — no SkiaSharp public-API changes were needed; no SkiaApi.generated.cs deltas.
Threading / disposal patterns	No changes.

There are no managed (C#) source changes in this PR.

Version / binding updates

File	Change
cgmanifest.json	chrome_milestone 150→151, commitHash updated to submodule HEAD, upstream_merge_commit updated to upstream m151 tip.
scripts/VERSIONS.txt	skia release m150→m151, libSkiaSharp milestone 150→151, libSkiaSharp soname 150.0.0→151.0.0, all SkiaSharp* NuGet entries bumped to 4.151.0, SkiaSharp assembly/file version bumped to 4.151.0.0.
scripts/azure-templates-variables.yml	SKIASHARP_VERSION → 4.151.0.
externals/skia	Submodule pointer updated.
binding/SkiaSharp/SkiaApi.generated.cs and friends	Regenerated. No diffs.

Native build changes (cross-platform — please review)

Added skia_use_partition_alloc=false to the gn args in every clang platform's native/**/build.cake:

• native/linux/build.cake — both libSkiaSharp and libHarfBuzzSharp GnNinja calls.
• native/wasm/build.cake — both libSkiaSharp and libHarfBuzzSharp GnNinja calls.
• native/macos/build.cake, native/tvos/build.cake, native/ios/build.cake, native/windows/build.cake, native/tizen/build.cake, native/android/build.cake — libSkiaSharp GnNinja calls only (HarfBuzzSharp on these platforms uses xcodebuild / msbuild / ndk-build / tizen, not gn).

Why: m151 introduced src/partition_alloc/, whose BUILD.gn by default tries to import ${skia_partition_alloc_dir}/partition_alloc.gni. Our DEPS does not vendor partition_alloc (it stays commented out), so we explicitly opt into the noop fallback shipped in src/partition_alloc/noop/. The default value of skia_use_partition_alloc is is_clang, which evaluates to true for every platform we ship, so the override is required. Per .agents/skills/update-skia/references/known-gotchas.md #23, the arg lives in build.cake rather than being passed via --gnArgs.

Build & test results

This automated workflow only built Linux x64:

• dotnet cake --target=externals-linux --arch=x64 → built libSkiaSharp.so.151.0.0 (10.8 MB) and libHarfBuzzSharp.so.0.61421.0 (2.7 MB) successfully.
• dotnet build binding/SkiaSharp/SkiaSharp.csproj → 0 errors, 0 warnings.
• pwsh ./utils/generate.ps1 (via regenerate-bindings.ps1) → no binding diffs.
• dotnet test tests/SkiaSharp.Tests.Console/SkiaSharp.Tests.Console.csproj → 5,584 passed, 0 failed, 172 skipped (skips are pre-existing GPU/headless related). Full log uploaded as test-output.txt artifact.

Items needing human attention

• Cross-platform native build verification. Only Linux x64 was built here. Please confirm that the skia_use_partition_alloc=false gn arg works correctly on Windows, macOS, iOS, tvOS, Android, Tizen, and WASM CI builds before merging — this is the primary risk of this sync.
• DEPS manual merge in the submodule PR preserves our pinned versions for everything tracked in cgmanifest.json. Worth a quick eye over mono/skia#skia-sync/m151 to confirm no required upstream dep was accidentally dropped.
• Submodule companion PR in mono/skia carries the merge + the sk_font.cpp include-path fix and must merge first (or at the same time) — the parent commit pins the submodule to that branch's HEAD.

Created by skia-upstream-sync.

[github-actions]

📦 Try the packages from this PR

Warning

Do not run these scripts without first reviewing the code in this PR.

Step 1 — Download the packages

bash / macOS / Linux:

curl -fsSL https://raw.githubusercontent.com/mono/SkiaSharp/main/scripts/get-skiasharp-pr.sh | bash -s -- 4294

PowerShell / Windows:

iex "& { $(irm https://raw.githubusercontent.com/mono/SkiaSharp/main/scripts/get-skiasharp-pr.ps1) } 4294"

Step 2 — Add the local NuGet source

dotnet nuget add source ~/.skiasharp/hives/pr-4294/packages --name skiasharp-pr-4294

More options

Option	Description
--successful-only / -SuccessfulOnly	Only use successful builds
--force / -Force	Overwrite previously downloaded packages
--list / -List	List available artifacts without downloading
--build-id ID / -BuildId ID	Download from a specific build

Or download manually from Azure Pipelines — look for the nuget artifact on the build for this PR.

Remove the source when you're done:

dotnet nuget remove source skiasharp-pr-4294

[github-actions]

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