[deoptimizer] Remove obsolete DeoptInfo::mnemonic field.

src/deoptimizer.h

Index: src/deoptimizer.h
diff --git a/src/deoptimizer.h b/src/deoptimizer.h
index 21ca84ed5271134c020e8b2c02aad19cab6c4890..99ebd3f9c6d09d1436c97f7c6159bf0489e6c19d 100644
--- a/src/deoptimizer.h
+++ b/src/deoptimizer.h
@@ -410,11 +410,10 @@ class Deoptimizer : public Malloced {
   static const char* GetDeoptReason(DeoptReason deopt_reason);
 
   struct DeoptInfo {
-    DeoptInfo(SourcePosition position, const char* m, DeoptReason d)
-        : position(position), mnemonic(m), deopt_reason(d), inlining_id(0) {}
+    DeoptInfo(SourcePosition position, DeoptReason d)
+        : position(position), deopt_reason(d), inlining_id(0) {}
 
     SourcePosition position;
-    const char* mnemonic;
     DeoptReason deopt_reason;
     int inlining_id;
   };