[debugger] add precise mode for code coverage.

src/feedback-vector-inl.h

Index: src/feedback-vector-inl.h
diff --git a/src/feedback-vector-inl.h b/src/feedback-vector-inl.h
index c704e700670028a2335df9685167d636592a38d2..4bab1f50e41e1f691630e776c8f6da2fa782bbca 100644
--- a/src/feedback-vector-inl.h
+++ b/src/feedback-vector-inl.h
@@ -96,6 +96,10 @@ int FeedbackVector::invocation_count() const {
   return Smi::cast(get(kInvocationCountIndex))->value();
 }
 
+void FeedbackVector::clear_invocation_count() {
+  set(kInvocationCountIndex, Smi::kZero);
+}
+
 // Conversion from an integer index to either a slot or an ic slot.
 // static
 FeedbackSlot FeedbackVector::ToSlot(int index) {