[tracing] Fix single-process detection logic of ChildTraceMessageFilter

base/trace_event/memory_dump_manager.cc

Index: base/trace_event/memory_dump_manager.cc
diff --git a/base/trace_event/memory_dump_manager.cc b/base/trace_event/memory_dump_manager.cc
index ac79144f9fdb27d7830c1b26c977bd952b1e5824..ed965fa2b312a8ccc40a0fcd95be2acc485fa8ed 100644
--- a/base/trace_event/memory_dump_manager.cc
+++ b/base/trace_event/memory_dump_manager.cc
@@ -77,10 +77,7 @@ void MemoryDumpManager::Initialize() {
 
 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;
 }