Remove the debugger_ field from Isolate in a PRODUCT build

runtime/vm/flow_graph_compiler.cc

Index: runtime/vm/flow_graph_compiler.cc
diff --git a/runtime/vm/flow_graph_compiler.cc b/runtime/vm/flow_graph_compiler.cc
index 85d27f6d51c72b753f4fb0e96b1fd65138b057ba..750541cb3e2f3fd780bcde9596e1b1cbfba52b70 100644
--- a/runtime/vm/flow_graph_compiler.cc
+++ b/runtime/vm/flow_graph_compiler.cc
@@ -85,7 +85,6 @@ static void PrecompilationModeHandler(bool value) {
     // Set flags affecting runtime accordingly for dart_bootstrap.
     // These flags are constants with PRODUCT and DART_PRECOMPILED_RUNTIME.
     FLAG_collect_code = false;
-    FLAG_support_debugger = false;
     FLAG_deoptimize_alot = false;  // Used in some tests.
     FLAG_deoptimize_every = 0;     // Used in some tests.
     FLAG_load_deferred_eagerly = true;