blink_gc_plugin: always enable warn_stack_allocated_trace_method check.

tools/clang/blink_gc_plugin/BlinkGCPluginOptions.h

Index: tools/clang/blink_gc_plugin/BlinkGCPluginOptions.h
diff --git a/tools/clang/blink_gc_plugin/BlinkGCPluginOptions.h b/tools/clang/blink_gc_plugin/BlinkGCPluginOptions.h
index 0df51cd597cc73c3f310ba54e6fb174a3f8a2a29..7ae95ea7b142cc4cfb859fb47f9e6d03f78ce928 100644
--- a/tools/clang/blink_gc_plugin/BlinkGCPluginOptions.h
+++ b/tools/clang/blink_gc_plugin/BlinkGCPluginOptions.h
@@ -14,7 +14,7 @@ struct BlinkGCPluginOptions {
 
   // If |true|, emit warning if stack allocated class types provide
   // a trace method.
-  bool warn_stack_allocated_trace_method = false;
+  bool warn_stack_allocated_trace_method = true;

[Nico, 2017/03/02 14:18:21]

I think you can remove this completely and pretend it's true everywhere where it
currently is (and accept the flag but make it a no-op)

[sof, 2017/03/02 14:23:21]

Does it matter much? we'll have to be back one more time in any case.

[Nico, 2017/03/02 14:26:49]

Doesn't matter too much but at the moment (after the patch) it'll be possible to
turn off the feature with a flag, so if we roll this version in someone could
conceivably turn off the feature somewhere, and then when we roll once more with
the flag gone completely they'd break. If the flag has no effect at all after
this patch here, then this can't happen. It's a super unlikely failure case
though.

   // If |true|, emit warning for class types which derive from from
   // GarbageCollectedFinalized<> when just GarbageCollected<> will do.
   bool warn_unneeded_finalizer = false;