Convert //ios from scoped_ptr to std::unique_ptr.

ios/web/public/web_thread.h

Index: ios/web/public/web_thread.h
diff --git a/ios/web/public/web_thread.h b/ios/web/public/web_thread.h
index 7c7195656d73e8fc30b3a04d724792af202447c8..7f7c4149b08f982eb78ddf40189e9437c352421a 100644
--- a/ios/web/public/web_thread.h
+++ b/ios/web/public/web_thread.h
@@ -217,9 +217,9 @@ class WebThread {
   // Returns an appropriate error message for when DCHECK_CURRENTLY_ON() fails.
   static std::string GetDCheckCurrentlyOnErrorMessage(ID expected);
 
-  // Use these templates in conjunction with RefCountedThreadSafe or scoped_ptr
-  // when you want to ensure that an object is deleted on a specific thread.
-  // This is needed when an object can hop between threads
+  // Use these templates in conjunction with RefCountedThreadSafe or
+  // std::unique_ptr when you want to ensure that an object is deleted on a
+  // specific thread. This is needed when an object can hop between threads
   // (i.e. IO -> FILE -> IO), and thread switching delays can mean that the
   // final IO tasks executes before the FILE task's stack unwinds.
   // This would lead to the object destructing on the FILE thread, which often
@@ -257,8 +257,8 @@ class WebThread {
   //
   //   ~Foo();
   //
-  // Sample usage with scoped_ptr:
-  // scoped_ptr<Foo, web::WebThread::DeleteOnIOThread> ptr;
+  // Sample usage with std::unique_ptr:
+  // std::unique_ptr<Foo, web::WebThread::DeleteOnIOThread> ptr;
   struct DeleteOnUIThread : public DeleteOnThread<UI> {};
   struct DeleteOnIOThread : public DeleteOnThread<IO> {};
   struct DeleteOnFileThread : public DeleteOnThread<FILE> {};