Use array<uint8> rather than string to pass BroadcastChannel messages.

content/browser/broadcast_channel/broadcast_channel_provider.h

 // 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.
 
 #ifndef CONTENT_BROWSER_BROADCAST_CHANNEL_BROADCAST_CHANNEL_PROVIDER_H_
 #define CONTENT_BROWSER_BROADCAST_CHANNEL_BROADCAST_CHANNEL_PROVIDER_H_
 
 #include <map>
 
 #include "base/memory/ref_counted.h"
@@ skipping 18 matching lines @@
       blink::mojom::BroadcastChannelClientAssociatedRequest connection)
           override;
 
  private:
   friend class base::RefCountedThreadSafe<BroadcastChannelProvider>;
   class Connection;
 
   ~BroadcastChannelProvider() override;
 
   void UnregisterConnection(Connection*);
-  void ReceivedMessageOnConnection(Connection*, const mojo::String& message);
+  void ReceivedMessageOnConnection(Connection*, mojo::Array<uint8_t> message);
 
   mojo::BindingSet<blink::mojom::BroadcastChannelProvider> bindings_;
   std::map<url::Origin, std::multimap<std::string, std::unique_ptr<Connection>>>
       connections_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_BROADCAST_CHANNEL_BROADCAST_CHANNEL_PROVIDER_H_