[AST] Keep track of the left brace source location of a tag decl.

This is useful for source modification tools. There will be a follow-up commit using it.

llvm-svn: 275590
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 4d75f80..6a21395 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -1018,9 +1018,7 @@
     }
   }
 
-  // FIXME: Fixup LBraceLoc
-  SemaRef.ActOnEnumBody(Enum->getLocation(), SourceLocation(),
-                        Enum->getRBraceLoc(), Enum,
+  SemaRef.ActOnEnumBody(Enum->getLocation(), Enum->getBraceRange(), Enum,
                         Enumerators,
                         nullptr, nullptr);
 }