Reduce FOR_EACH_OBSERVER usage in extensions

extensions/browser/api/display_source/display_source_apitestbase.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "extensions/browser/api/display_source/display_source_apitestbase.h"
 
 #include <list>
 #include <map>
 #include <utility>
 
@@ skipping 388 matching lines @@
 }
 
 void MockDisplaySourceConnectionDelegate::OnSinkConnected() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   CHECK(active_sink_);
   active_sink_->state = SINK_STATE_CONNECTED;
   NotifySinksUpdated();
 }
 
 void MockDisplaySourceConnectionDelegate::NotifySinksUpdated() {
-  FOR_EACH_OBSERVER(DisplaySourceConnectionDelegate::Observer, observers_,
-                    OnSinksUpdated(sinks_));
+  for (auto& observer : observers_)
+    observer.OnSinksUpdated(sinks_);
 }
 
 void MockDisplaySourceConnectionDelegate::
 EnqueueSinkMessage(std::string message) {
   const std::size_t found_session_key = message.find(kSessionKey);
   if (found_session_key != std::string::npos)
     AdaptMessagePattern(found_session_key, kSessionKey, kSessionIdLength,
                         session_id_, message);
 
   const std::size_t found_unicast_key = message.find(kUnicastKey);
@@ skipping 105 matching lines @@
         base::Bind(&MockDisplaySourceConnectionDelegate::Disconnect,
                    base::Unretained(this), StringCallback()));
     return;
    }
 
   DCHECK(socket_.get());
   ReceiveMediaPacket();
 }
 
 }  // namespace extensions