Remove redundant FunctionDecl argument from a couple functions.

This argument was added in r254554 in order to support the
pass_object_size attribute. However, in r296076, the attribute's
presence is now also represented in FunctionProtoType's
ExtParameterInfo, and thus it's unnecessary to pass along a separate
FunctionDecl.

The functions modified are:
 RequiredArgs::forPrototype{,Plus}, and
 CodeGenTypes::ConvertFunctionType.

After this, it's also (again) unnecessary to have a separate
ConvertFunctionType function ConvertType, so convert callers back to
the latter, leaving the former as an internal helper function.

llvm-svn: 352946
diff --git a/clang/lib/CodeGen/CGExprCXX.cpp b/clang/lib/CodeGen/CGExprCXX.cpp
index 8aa8436..1f650ae 100644
--- a/clang/lib/CodeGen/CGExprCXX.cpp
+++ b/clang/lib/CodeGen/CGExprCXX.cpp
@@ -54,7 +54,7 @@
   }
 
   const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>();
-  RequiredArgs required = RequiredArgs::forPrototypePlus(FPT, Args.size(), MD);
+  RequiredArgs required = RequiredArgs::forPrototypePlus(FPT, Args.size());
   unsigned PrefixSize = Args.size() - 1;
 
   // And the rest of the call args.
@@ -452,8 +452,7 @@
   // Push the this ptr.
   Args.add(RValue::get(ThisPtrForCall), ThisType);
 
-  RequiredArgs required =
-      RequiredArgs::forPrototypePlus(FPT, 1, /*FD=*/nullptr);
+  RequiredArgs required = RequiredArgs::forPrototypePlus(FPT, 1);
 
   // And the rest of the call args
   EmitCallArgs(Args, FPT, E->arguments());