Remove unused start_unanchored_ member from DFA class.

This is a followup to d69e99b.

Change-Id: I6b714168b988de0c38d6ae481cf0477fc4115c0d
Reviewed-on: https://code-review.googlesource.com/2942
Reviewed-by: Paul Wankadia <junyer@google.com>

re2/dfa.cc

diff --git a/re2/dfa.cc b/re2/dfa.cc
index a8fc625..25e0220 100644
--- a/re2/dfa.cc
+++ b/re2/dfa.cc
@@ -339,7 +339,6 @@
   // Constant after initialization.
   Prog* prog_;              // The regular expression program to run.
   Prog::MatchKind kind_;    // The kind of DFA.
-  int start_unanchored_;  // start of unanchored program
   bool init_failed_;        // initialization failed (out of memory)
 
   Mutex mutex_;  // mutex_ >= cache_mutex_.r
@@ -442,11 +441,8 @@
   if (DebugDFA)
     fprintf(stderr, "\nkind %d\n%s\n", (int)kind_, prog_->DumpUnanchored().c_str());
   int nmark = 0;
-  start_unanchored_ = 0;
-  if (kind_ == Prog::kLongestMatch) {
+  if (kind_ == Prog::kLongestMatch)
     nmark = prog->size();
-    start_unanchored_ = prog->start_unanchored();
-  }
   nastack_ = 2 * prog->size() + nmark;
 
   // Account for space needed for DFA, q0, q1, astack.