Fix an assertion ted was hitting, due to an uninitialized variable.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@49678 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Rewrite/RewriteRope.cpp

@@ -53,7 +53,7 @@ namespace {
     /// is an instance of RopePieceBTreeInterior.
     bool IsLeaf;
     
-    RopePieceBTreeNode(bool isLeaf) : IsLeaf(isLeaf) {}
+    RopePieceBTreeNode(bool isLeaf) : Size(0), IsLeaf(isLeaf) {}
     ~RopePieceBTreeNode() {}
   public: