Use SmallVectorImpl& instead of SmallVector to avoid repeating small vector size.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186098 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Bitcode/Writer/ValueEnumerator.h b/lib/Bitcode/Writer/ValueEnumerator.h
index 0af6164..d1ca15f 100644
--- a/lib/Bitcode/Writer/ValueEnumerator.h
+++ b/lib/Bitcode/Writer/ValueEnumerator.h
@@ -125,7 +125,7 @@
 
   const ValueList &getValues() const { return Values; }
   const ValueList &getMDValues() const { return MDValues; }
-  const SmallVector<const MDNode *, 8> &getFunctionLocalMDValues() const {
+  const SmallVectorImpl<const MDNode *> &getFunctionLocalMDValues() const {
     return FunctionLocalMDs;
   }
   const TypeList &getTypes() const { return Types; }