blink_gc_plugin: always enable warn_stack_allocated_trace_method check.

tools/clang/blink_gc_plugin/BlinkGCPluginOptions.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef TOOLS_BLINK_GC_PLUGIN_BLINK_GC_PLUGIN_OPTIONS_H_
 #define TOOLS_BLINK_GC_PLUGIN_BLINK_GC_PLUGIN_OPTIONS_H_
 
 #include <set>
 #include <string>
 #include <vector>
 
 struct BlinkGCPluginOptions {
   bool dump_graph = false;
 
   // 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;
 
   // TODO(https://crbug.com/675879): Clean up after the Blink rename.
   bool use_chromium_style_naming = false;
 
   std::set<std::string> ignored_classes;
   std::set<std::string> checked_namespaces;
   std::vector<std::string> ignored_directories;
 };
 
 #endif  // TOOLS_BLINK_GC_PLUGIN_BLINK_GC_PLUGIN_OPTIONS_H_