[debug] do not report unnecessary coverage data.

src/debug/debug-coverage.h

Index: src/debug/debug-coverage.h
diff --git a/src/debug/debug-coverage.h b/src/debug/debug-coverage.h
index e923fc4b21cb88a7d3b4b017a7042a12e02b27cd..b21622cb2eaf2f55196f8e32bb0fa7131d7e4019 100644
--- a/src/debug/debug-coverage.h
+++ b/src/debug/debug-coverage.h
@@ -27,7 +27,7 @@ struct CoverageFunction {
 
 struct CoverageScript {
   // Initialize top-level function in case it has been garbage-collected.
-  CoverageScript(Isolate* isolate, Handle<Script> s) : script(s) {}
+  explicit CoverageScript(Handle<Script> s) : script(s) {}
   Handle<Script> script;
   // Functions are sorted by start position, from outer to inner function.
   std::vector<CoverageFunction> functions;