[debugger] infrastructure for side-effect-free debug-evaluate.

src/flag-definitions.h

Index: src/flag-definitions.h
diff --git a/src/flag-definitions.h b/src/flag-definitions.h
index f3a3116daed22b5a34b850c8a972be3d912555d9..7ee98c2be1355511bda5cce898821497bae245b2 100644
--- a/src/flag-definitions.h
+++ b/src/flag-definitions.h
@@ -693,6 +693,11 @@ DEFINE_IMPLICATION(trace_array_abuse, trace_external_array_abuse)
 // debugger
 DEFINE_BOOL(trace_debug_json, false, "trace debugging JSON request/response")
 DEFINE_BOOL(enable_liveedit, true, "enable liveedit experimental feature")
+DEFINE_BOOL(side_effect_free_debug_evaluate, false,

[ofrobots, 2017/01/10 17:23:13]

A flag is fine for the prototype, but eventually would this be something that we
could configure at either the time the Debug context is created, or when
evaluate is called?

+            "use side-effect-free debug-evaluate for testing")
+DEFINE_BOOL(
+    trace_side_effect_free_debug_evaluate, false,
+    "print debug messages for side-effect-free debug-evaluate for testing")
 DEFINE_BOOL(hard_abort, true, "abort by crashing")
 
 // execution.cc