Update scoped_ptr references to be unique_ptr in src/base comments.

base/bind_helpers.h

Index: base/bind_helpers.h
diff --git a/base/bind_helpers.h b/base/bind_helpers.h
index 1e65225572906bbeadfac3f24330be29949d5955..7b3d7d34740e45433136339a109f73a29b545bb6 100644
--- a/base/bind_helpers.h
+++ b/base/bind_helpers.h
@@ -21,7 +21,7 @@
 // Owned() transfers ownership of an object to the Callback resulting from
 // bind; the object will be deleted when the Callback is deleted.
 //
-// Passed() is for transferring movable-but-not-copyable types (eg. scoped_ptr)
+// Passed() is for transferring movable-but-not-copyable types (eg. unique_ptr)
 // through a Callback. Logically, this signifies a destructive transfer of
 // the state of the argument into the target function.  Invoking
 // Callback::Run() twice on a Callback that was created with a Passed()