Make Callback::Reset() return a copy to support use-cases where Run() ends up modifying |*this|.

media/base/filters.cc

Index: media/base/filters.cc
diff --git a/media/base/filters.cc b/media/base/filters.cc
index 620b5e58140a35f310900909a8aa0ee021f85d2b..aa1588b1ef225725d221243295dfe5155848d039 100644
--- a/media/base/filters.cc
+++ b/media/base/filters.cc
@@ -8,20 +8,6 @@
 
 namespace media {
 
-void ResetAndRunCB(FilterStatusCB* cb, PipelineStatus status) {
-  DCHECK(!cb->is_null());
-  FilterStatusCB tmp_cb(*cb);
-  cb->Reset();
-  tmp_cb.Run(status);
-}
-
-void ResetAndRunCB(base::Closure* cb) {
-  DCHECK(!cb->is_null());
-  base::Closure tmp_cb(*cb);
-  cb->Reset();
-  tmp_cb.Run();
-}
-
 Filter::Filter() : host_(NULL) {}
 
 Filter::~Filter() {}