Add SkRasterPipeline blitter.

This is now pixel-exact with the existing sRGB SW impl as far as I've tested.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2146413002
CQ_INCLUDE_TRYBOTS=master.client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot,Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Debug-ASAN-Trybot

Committed: https://skia.googlesource.com/skia/+/3011e337693a9786f62d8de9ac4b239ad6dbdaca
Review-Url: https://codereview.chromium.org/2146413002
diff --git a/src/core/SkCoreBlitters.h b/src/core/SkCoreBlitters.h
index 8fcfde6..46b2b7e 100644
--- a/src/core/SkCoreBlitters.h
+++ b/src/core/SkCoreBlitters.h
@@ -210,4 +210,8 @@
                                 SkShader::Context* shaderContext,
                                 SkTBlitterAllocator* allocator);
 
+
+// Returns nullptr if no SkRasterPipeline blitter can be constructed for this paint.
+SkBlitter* SkCreateRasterPipelineBlitter(const SkPixmap&, const SkPaint&, SkTBlitterAllocator*);
+
 #endif