Add shader based blending of kPlus for configs that need clamping

This effectively reverts https://skia-review.googlesource.com/c/skia/+/140500
and relands https://skia-review.googlesource.com/c/skia/+/48183.

Bug: skia:8871
Change-Id: I6b1d5daa3d319e0c078e553926ed9166cca9a24a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/199930
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
diff --git a/src/gpu/GrProgramDesc.cpp b/src/gpu/GrProgramDesc.cpp
index 5401d4d..a066145 100644
--- a/src/gpu/GrProgramDesc.cpp
+++ b/src/gpu/GrProgramDesc.cpp
@@ -253,6 +253,7 @@
     SkASSERT(header->processorFeatures() == processorFeatures);  // Ensure enough bits.
     header->fSnapVerticesToPixelCenters = pipeline.snapVerticesToPixelCenters();
     header->fHasPointSize = hasPointSize ? 1 : 0;
-    header->fClampBlendInput = GrPixelConfigNeedsClamp(renderTarget->config()) ? 1 : 0;
+    header->fClampBlendInput =
+            GrClampType::kManual == GrPixelConfigClampType(renderTarget->config()) ? 1 : 0;
     return true;
 }