Force non-joinable SimpleThreads to be leaked.

base/threading/simple_thread.cc

Index: base/threading/simple_thread.cc
diff --git a/base/threading/simple_thread.cc b/base/threading/simple_thread.cc
index fa1a3449e057e2176244b092ab9b20b4ef88ba8e..0a0665631a2b14341ea277280fe6a46834d4253f 100644
--- a/base/threading/simple_thread.cc
+++ b/base/threading/simple_thread.cc
@@ -23,9 +23,10 @@ SimpleThread::SimpleThread(const std::string& name_prefix,
              WaitableEvent::InitialState::NOT_SIGNALED) {}
 
 SimpleThread::~SimpleThread() {
+  DCHECK(options_.joinable) << "A non-joinable thread must be leaked.";
   DCHECK(HasBeenStarted()) << "SimpleThread was never started.";
-  DCHECK(thread_.is_null()) << "Joinable SimpleThread destroyed without being "
-                            << "Join()ed.";
+  DCHECK(HasBeenJoined()) << "Joinable SimpleThread destroyed without being "
+                          << "Join()ed.";
 }
 
 void SimpleThread::Start() {
@@ -41,9 +42,9 @@ void SimpleThread::Start() {
 }
 
 void SimpleThread::Join() {
+  DCHECK(options_.joinable) << "A non-joinable thread can't be joined.";
   DCHECK(HasBeenStarted()) << "Tried to Join a never-started thread.";
   DCHECK(!HasBeenJoined()) << "Tried to Join a thread multiple times.";
-  DCHECK(!thread_.is_null()) << "A non-joinable thread can't be joined.";
   PlatformThread::Join(thread_);
   thread_ = PlatformThreadHandle();
   joined_ = true;