Fix --trace-shutdown with thread-local tracing.

base/debug/trace_event_impl.cc

 // Copyright (c) 2012 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 "base/debug/trace_event_impl.h"
 
 #include <algorithm>
 
 #include "base/base_switches.h"
 #include "base/bind.h"
@@ skipping 1336 matching lines @@
 // 4. If any thread hasn't finish its flush in time, finish the flush.
 void TraceLog::Flush(const TraceLog::OutputCallback& cb) {
   if (IsEnabled()) {
     // Can't flush when tracing is enabled because otherwise PostTask would
     // - it generates more trace events;
     // - it deschedules the calling thread on some platforms causing inaccurate
     //   timing of the trace events.
     scoped_refptr<RefCountedString> empty_result = new RefCountedString;
     if (!cb.is_null())
       cb.Run(empty_result, false);
+    LOG(WARNING) << "Ignored TraceLog::Flush called when tracing is enabled";
     return;
   }
 
   int flush_count;
   {
     AutoLock lock(lock_);
     flush_count = ++flush_count_;
     DCHECK(!flush_message_loop_proxy_.get());
     flush_message_loop_proxy_ = MessageLoopProxy::current();
     DCHECK(!thread_message_loops_.size() || flush_message_loop_proxy_.get());
@@ skipping 664 matching lines @@
         0,                       // num_args
         NULL,                    // arg_names
         NULL,                    // arg_types
         NULL,                    // arg_values
         NULL,                    // convertable values
         TRACE_EVENT_FLAG_NONE);  // flags
   }
 }
 
 }  // namespace trace_event_internal