Constify the 'dump' method so that it can be called by a const object.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182620 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/Driver/ArgList.h b/include/clang/Driver/ArgList.h
index 9db170c..777d052 100644
--- a/include/clang/Driver/ArgList.h
+++ b/include/clang/Driver/ArgList.h
@@ -300,7 +300,7 @@
 
     /// @}
 
-    void dump();
+    void dump() const;
   };
 
   class InputArgList : public ArgList  {
diff --git a/lib/Driver/ArgList.cpp b/lib/Driver/ArgList.cpp
index 4b8d151..0033927 100644
--- a/lib/Driver/ArgList.cpp
+++ b/lib/Driver/ArgList.cpp
@@ -321,11 +321,10 @@
   return MakeArgString(LHS + RHS);
 }
 
-void ArgList::dump() {
+void ArgList::dump() const {
   llvm::errs() << "ArgList:";
-  for (iterator it = begin(), ie = end(); it != ie; ++it) {
+  for (const_iterator it = begin(), ie = end(); it != ie; ++it)
     llvm::errs() << " " << (*it)->getSpelling();
-  }
   llvm::errs() << "\n";
 }