[debugger] remove step count parameter from prepare step.

test/mjsunit/debug-continue.js

Index: test/mjsunit/debug-continue.js
diff --git a/test/mjsunit/debug-continue.js b/test/mjsunit/debug-continue.js
index 1d0be637ff149b072df39d3ed7b620e69ac6ea39..55bbb29b1d246acc3476695aa22cd1ab7af695c4 100644
--- a/test/mjsunit/debug-continue.js
+++ b/test/mjsunit/debug-continue.js
@@ -74,12 +74,14 @@ function listener(event, exec_state, event_data, data) {
 
     // Test some illegal continue requests.
     testArguments(exec_state, '{"stepaction":"maybe"}', false);
-    testArguments(exec_state, '{"stepcount":-1}', false);
 
     // Test some legal continue requests.
     testArguments(exec_state, '{"stepaction":"in"}', true);
     testArguments(exec_state, '{"stepaction":"next"}', true);
     testArguments(exec_state, '{"stepaction":"out"}', true);
+
+    // Step count argument is ignored.
+    testArguments(exec_state, '{"stepcount":-1}', true);
     testArguments(exec_state, '{"stepcount":1}', true);
     testArguments(exec_state, '{"stepcount":10}', true);
     testArguments(exec_state, '{"stepcount":"10"}', true);