[libFuzzer] refactor the merging code, NFC

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk/lib/fuzzer@353576 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/FuzzerMerge.h b/FuzzerMerge.h
index 273f486..0d35155 100644
--- a/FuzzerMerge.h
+++ b/FuzzerMerge.h
@@ -71,7 +71,8 @@
 
 Vector<std::string>
 CrashResistantMerge(const Vector<std::string> &Args,
-                    const Vector<std::string> &Corpora,
+                    const Vector<SizedFile> &OldCorpus,
+                    const Vector<SizedFile> &NewCorpus,
                     const std::string &CFPath);
 
 }  // namespace fuzzer