Add CK_DerivedToBase and use it PerformObjectMemberConversion.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@77652 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index ff3b4ef..0880d10 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -2016,7 +2016,7 @@
                                    From->getSourceRange()))
     return true;
 
-  ImpCastExprToType(From, DestType, /*isLvalue=*/true);
+  ImpCastExprToType(From, DestType, CastExpr::CK_Unknown, /*isLvalue=*/true);
   return false;
 }
 
@@ -4476,6 +4476,7 @@
     // FIXME: Represent the user-defined conversion in the AST!
     ImpCastExprToType(Object,
                       Conv->getConversionType().getNonReferenceType(),
+                      CastExpr::CK_Unknown,
                       Conv->getConversionType()->isLValueReferenceType());
     return ActOnCallExpr(S, ExprArg(*this, Object), LParenLoc,
                          MultiExprArg(*this, (ExprTy**)Args, NumArgs),