[tracing] Fix single-process detection logic of ChildTraceMessageFilter

base/trace_event/memory_dump_manager.cc

 // 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 "base/trace_event/memory_dump_manager.h"
 
 #include <algorithm>
 
 #include "base/atomic_sequence_num.h"
 #include "base/compiler_specific.h"
@@ skipping 59 matching lines @@
   base::trace_event::TraceLog::GetInstance()->RemoveEnabledStateObserver(this);
 }
 
 void MemoryDumpManager::Initialize() {
   TRACE_EVENT0(kTraceCategory, "init");  // Add to trace-viewer category list.
   trace_event::TraceLog::GetInstance()->AddEnabledStateObserver(this);
 }
 
 void MemoryDumpManager::SetDelegate(MemoryDumpManagerDelegate* delegate) {
   AutoLock lock(lock_);
-  // TODO(primiano): The DCHECK below is disabled just temporary (and it is
-  // strongly useful). It should be re-enabled soon as crbug.com/474973 is fixed
-  // (ETA: end of April 2015). Commenting out just to de-entangle CL deps.
-  // DCHECK(delegate_ == nullptr);
+  DCHECK(delegate_ == nullptr);

[Avi (use Gerrit), 2015/04/08 14:42:35]

DCHECK_EQ(nullptr, delegate);

[Primiano Tucci (use gerrit), 2015/04/08 15:04:29]

Yeah, I was just too lazy to do the cast.
Unfortunately you can't just DCHECK_EQ(nullptr,stuff) as it will fail to find
the right template expansion (with a nice 10 pages error).
This is the only way I know of using DCHECK_EQ with nullptr.

[Avi (use Gerrit), 2015/04/08 15:20:19]

That's surprising; I've done it quite a bit. You couldn't do it with NULL, but
nullptr should work.

   delegate_ = delegate;
 }
 
 void MemoryDumpManager::RegisterDumpProvider(MemoryDumpProvider* mdp) {
   AutoLock lock(lock_);
   if (std::find(dump_providers_registered_.begin(),
                 dump_providers_registered_.end(),
                 mdp) != dump_providers_registered_.end()) {
     return;
   }
@@ skipping 112 matching lines @@
 }
 
 void MemoryDumpManager::OnTraceLogDisabled() {
   AutoLock lock(lock_);
   dump_providers_enabled_.clear();
   subtle::NoBarrier_Store(&memory_tracing_enabled_, 0);
 }
 
 }  // namespace trace_event
 }  // namespace base