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 cc7889f0488706ce669819d6acbd211d2d135371..d0248c90faf1bf39847690b67d04fd9635393bb2 100644
--- a/base/observer_list_unittest.cc
+++ b/base/observer_list_unittest.cc
@@ -118,7 +118,7 @@ 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);
@@ -146,7 +146,7 @@ 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() {