remove const_cast.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@108803 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Checker/CFRefCount.cpp b/lib/Checker/CFRefCount.cpp
index 3c74cd8..d35f247 100644
--- a/lib/Checker/CFRefCount.cpp
+++ b/lib/Checker/CFRefCount.cpp
@@ -82,8 +82,7 @@
 
 static const ObjCMethodDecl*
 ResolveToInterfaceMethodDecl(const ObjCMethodDecl *MD) {
-  ObjCInterfaceDecl *ID =
-    const_cast<ObjCInterfaceDecl*>(MD->getClassInterface());
+  const ObjCInterfaceDecl *ID = MD->getClassInterface();
 
   return MD->isInstanceMethod()
          ? ID->lookupInstanceMethod(MD->getSelector())