InstrProf: Actually detect bad headers

<rdar://problem/15950346>

llvm-svn: 204510
diff --git a/llvm/lib/ProfileData/InstrProf.cpp b/llvm/lib/ProfileData/InstrProf.cpp
index ecabdd7..850f613 100644
--- a/llvm/lib/ProfileData/InstrProf.cpp
+++ b/llvm/lib/ProfileData/InstrProf.cpp
@@ -29,6 +29,8 @@
       return "End of File";
     case instrprof_error::bad_magic:
       return "Invalid file format (bad magic)";
+    case instrprof_error::bad_header:
+      return "Invalid header";
     case instrprof_error::unsupported_version:
       return "Unsupported format version";
     case instrprof_error::too_large: