blink_gc_plugin: warn of unused trace methods to stack allocated classes.

tools/clang/blink_gc_plugin/BlinkGCPluginConsumer.cpp

 // 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.
 
 #include "BlinkGCPluginConsumer.h"
 
 #include <algorithm>
 #include <set>
 
 #include "CheckDispatchVisitor.h"
@@ skipping 163 matching lines @@
   }
 
   CheckClass(info);
 }
 
 void BlinkGCPluginConsumer::CheckClass(RecordInfo* info) {
   if (!info)
     return;
 
   if (CXXMethodDecl* trace = info->GetTraceMethod()) {
+    if (options_.warn_stack_allocated_trace_method && info->IsStackAllocated())
+      reporter_.TraceMethodForStackAllocatedClass(info, trace);
     if (trace->isPure())
       reporter_.ClassDeclaresPureVirtualTrace(info, trace);
   } else if (info->RequiresTraceMethod()) {
     reporter_.ClassRequiresTraceMethod(info);
   }
 
   // Check polymorphic classes that are GC-derived or have a trace method.
   if (info->record()->hasDefinition() && info->record()->isPolymorphic()) {
     // TODO: Check classes that inherit a trace method.
     CXXMethodDecl* trace = info->GetTraceMethod();
@@ skipping 521 matching lines @@
   SourceLocation spelling_location = source_manager.getSpellingLoc(loc);
   PresumedLoc ploc = source_manager.getPresumedLoc(spelling_location);
   if (ploc.isInvalid()) {
     // If we're in an invalid location, we're looking at things that aren't
     // actually stated in the source.
     return false;
   }
   *filename = ploc.getFilename();
   return true;
 }