[debugger] debug-evaluate should not not modify local values.

src/flag-definitions.h

Index: src/flag-definitions.h
diff --git a/src/flag-definitions.h b/src/flag-definitions.h
index b98b9952613404e352565e01baefa06fdae0e446..b42849e354a4cf655b8cbc2bdcae3f87cd4439c0 100644
--- a/src/flag-definitions.h
+++ b/src/flag-definitions.h
@@ -597,8 +597,7 @@ DEFINE_BOOL(cache_prototype_transitions, true, "cache prototype transitions")
 DEFINE_INT(cpu_profiler_sampling_interval, 1000,
            "CPU profiler sampling interval in microseconds")
 
-// debug.cc
-DEFINE_BOOL(trace_debug_json, false, "trace debugging JSON request/response")
+// Array abuse tracing
 DEFINE_BOOL(trace_js_array_abuse, false,
             "trace out-of-bounds accesses to JS arrays")
 DEFINE_BOOL(trace_external_array_abuse, false,
@@ -607,6 +606,11 @@ DEFINE_BOOL(trace_array_abuse, false,
             "trace out-of-bounds accesses to all arrays")
 DEFINE_IMPLICATION(trace_array_abuse, trace_js_array_abuse)
 DEFINE_IMPLICATION(trace_array_abuse, trace_external_array_abuse)
+
+// debugger
+DEFINE_BOOL(debug_eval_readonly_locals, true,
+            "do not update locals after debug-evaluate")
+DEFINE_BOOL(trace_debug_json, false, "trace debugging JSON request/response")
 DEFINE_BOOL(enable_liveedit, true, "enable liveedit experimental feature")
 DEFINE_BOOL(hard_abort, true, "abort by crashing")