[libFuzzer] implement -focus_function=auto, to be used with Data Flow Traces

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk/lib/fuzzer@360378 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/FuzzerLoop.cpp b/FuzzerLoop.cpp
index fd5b226..d1ad3e3 100644
--- a/FuzzerLoop.cpp
+++ b/FuzzerLoop.cpp
@@ -157,8 +157,9 @@
   AllocateCurrentUnitData();
   CurrentUnitSize = 0;
   memset(BaseSha1, 0, sizeof(BaseSha1));
-  TPC.SetFocusFunction(Options.FocusFunction);
-  DFT.Init(Options.DataFlowTrace, Options.FocusFunction);
+  auto FocusFunctionOrAuto = Options.FocusFunction;
+  DFT.Init(Options.DataFlowTrace, &FocusFunctionOrAuto , MD.GetRand());
+  TPC.SetFocusFunction(FocusFunctionOrAuto);
 }
 
 Fuzzer::~Fuzzer() {}