Rewrite base::Bind into base::BindOnce on trivial cases in base

base/observer_list_unittest.cc

Index: base/observer_list_unittest.cc
diff --git a/base/observer_list_unittest.cc b/base/observer_list_unittest.cc
index c5e556bd9da4e76f65ad9965fb256d02932e672b..a4e443f8bf565b85f049e1be149cc9bf6f73a8ec 100644
--- a/base/observer_list_unittest.cc
+++ b/base/observer_list_unittest.cc
@@ -124,7 +124,7 @@ class AddRemoveThread : public PlatformThread::Delegate,
     loop_ = new MessageLoop();  // Fire up a message loop.
     loop_->task_runner()->PostTask(
         FROM_HERE,
-        base::Bind(&AddRemoveThread::AddTask, weak_factory_.GetWeakPtr()));
+        base::BindOnce(&AddRemoveThread::AddTask, weak_factory_.GetWeakPtr()));
     RunLoop().Run();
     delete loop_;
     loop_ = reinterpret_cast<MessageLoop*>(0xdeadbeef);
@@ -152,7 +152,7 @@ class AddRemoveThread : public PlatformThread::Delegate,
 
     loop_->task_runner()->PostTask(
         FROM_HERE,
-        base::Bind(&AddRemoveThread::AddTask, weak_factory_.GetWeakPtr()));
+        base::BindOnce(&AddRemoveThread::AddTask, weak_factory_.GetWeakPtr()));
   }
 
   void Quit() {