YAML: Fix the output of sequences that contain flow sequences.

This patch fixes a bug where the YAML Output class emitted
a sequence of flow sequences without the '-' characters.
Before:
  
  seq:
    [ a, b ]
    [ c, d ]

After:

  seq:
    - [ a, b ]
    - [ c, d ]


Reviewers: Justin Bogner

Differential Revision: http://reviews.llvm.org/D9206


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236329 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/YAMLTraits.cpp

@@ -633,7 +633,8 @@ void Output::newLineCheck() {
 
   if (StateStack.back() == inSeq) {
     OutputDash = true;
-  } else if ((StateStack.size() > 1) && (StateStack.back() == inMapFirstKey) &&
+  } else if ((StateStack.size() > 1) && ((StateStack.back() == inMapFirstKey) ||
+             (StateStack.back() == inFlowSeq)) &&
              (StateStack[StateStack.size() - 2] == inSeq)) {
     --Indent;
     OutputDash = true;