message: Future proofing MakeBlendMultiplier & MakeBlendOp
  Remove default from switch statements to trigger compile errors if MTL::BlendFactor or MTL::BlendOperation enumerations change in the future.
diff: @@ -47,7 +47,6 @@ BlendMultiplier MakeBlendMultiplier(MTL::BlendFactor blend)
  case MTL::BlendFactorOneMinusSource1Color: return BlendMultiplier::InvSrc1Col;
  case MTL::BlendFactorSource1Alpha: return BlendMultiplier::Src1Alpha;
  case MTL::BlendFactorOneMinusSource1Alpha: return BlendMultiplier::InvSrc1Alpha;
  - default: break;
  }
  return BlendMultiplier::One;
  @@ -62,7 +61,6 @@ BlendOperation MakeBlendOp(MTL::BlendOperation op)
  case MTL::BlendOperationReverseSubtract: return BlendOperation::ReversedSubtract;
  case MTL::BlendOperationMin: return BlendOperation::Minimum;
  case MTL::BlendOperationMax: return BlendOperation::Maximum;
  - default: break;
  }
  return BlendOperation::Add;
  