[wasm] Add inspector test for stepping

src/runtime/runtime-debug.cc

Index: src/runtime/runtime-debug.cc
diff --git a/src/runtime/runtime-debug.cc b/src/runtime/runtime-debug.cc
index 8d1e92d1e0721b4a8e1005a84bb4e8b7bdb158d2..fd142551ab05622f47b7e360288264640fa337ed 100644
--- a/src/runtime/runtime-debug.cc
+++ b/src/runtime/runtime-debug.cc
@@ -1666,7 +1666,8 @@ namespace {
 int ScriptLinePositionWithOffset(Handle<Script> script, int line, int offset) {
   if (line < 0 || offset < 0) return -1;
 
-  if (line == 0) return ScriptLinePosition(script, line) + offset;
+  if (line == 0 || offset == 0)
+    return ScriptLinePosition(script, line) + offset;
 
   Script::PositionInfo info;
   if (!Script::GetPositionInfo(script, offset, &info, Script::NO_OFFSET)) {