blink_gc_plugin: always enable warn_stack_allocated_trace_method check.

tools/clang/blink_gc_plugin/BlinkGCPlugin.cpp

Index: tools/clang/blink_gc_plugin/BlinkGCPlugin.cpp
diff --git a/tools/clang/blink_gc_plugin/BlinkGCPlugin.cpp b/tools/clang/blink_gc_plugin/BlinkGCPlugin.cpp
index 099b2bd96bdd4f2ad0fbaa71b28bd2fd26ea046f..5063e69e0b896272cc8e36c9acc9ecc8f6053484 100644
--- a/tools/clang/blink_gc_plugin/BlinkGCPlugin.cpp
+++ b/tools/clang/blink_gc_plugin/BlinkGCPlugin.cpp
@@ -34,6 +34,8 @@ class BlinkGCPluginAction : public PluginASTAction {
       if (arg == "dump-graph") {
         options_.dump_graph = true;
       } else if (arg == "warn-stack-allocated-trace-method") {
+        // TODO(sof): will be removed once a GC plugin binary has been rolled
+        // out with a |true| default for warn_stack_allocated_trace_method.
         options_.warn_stack_allocated_trace_method = true;
       } else if (arg == "warn-unneeded-finalizer") {
         options_.warn_unneeded_finalizer = true;