Use SmallVectorImpl instead of SmallVector for iterators and references to avoid specifying the vector size unnecessarily.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@185610 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Parse/ParseAST.cpp b/lib/Parse/ParseAST.cpp
index 7cd8a21..5678ece 100644
--- a/lib/Parse/ParseAST.cpp
+++ b/lib/Parse/ParseAST.cpp
@@ -145,7 +145,7 @@
   }
 
   // Process any TopLevelDecls generated by #pragma weak.
-  for (SmallVector<Decl*,2>::iterator
+  for (SmallVectorImpl<Decl *>::iterator
        I = S.WeakTopLevelDecls().begin(),
        E = S.WeakTopLevelDecls().end(); I != E; ++I)
     Consumer->HandleTopLevelDecl(DeclGroupRef(*I));