[debugger] correctly find source position of implicit return statement.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 67ccd31014249127b5aede7c3cc6be3cdfc7af5e..cebb4490c8c26af58875a407677de539ca695b8a 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -11354,8 +11354,10 @@ static void CalculateLineEndsImpl(Isolate* isolate,
 
   if (src_len > 0 && cache->IsLineTerminatorSequence(src[src_len - 1], 0)) {
     line_ends->Add(src_len - 1);
-  } else if (include_ending_line) {
-    // Even if the last line misses a line end, it is counted.
+  }
+  if (include_ending_line) {
+    // Include one character beyond the end of script. The rewriter uses that
+    // position for the implicit return statement.
     line_ends->Add(src_len);
   }
 }