Give CGDebugInfo::getContextDescriptor a more specific return type

Not that the DI* hierarchy is terribly type safe, but this makes the contract a
little clearer I think.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179835 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGDebugInfo.h b/lib/CodeGen/CGDebugInfo.h
index 3a0df99..060b738 100644
--- a/lib/CodeGen/CGDebugInfo.h
+++ b/lib/CodeGen/CGDebugInfo.h
@@ -281,7 +281,7 @@
                                             uint64_t *OffSet);
 
   /// getContextDescriptor - Get context info for the decl.
-  llvm::DIDescriptor getContextDescriptor(const Decl *Decl);
+  llvm::DIScope getContextDescriptor(const Decl *Decl);
 
   /// createRecordFwdDecl - Create a forward decl for a RecordType in a given
   /// context.