[cast_channel] Make CastSocket not inherit from ApiResource

extensions/browser/api/cast_channel/cast_test_util.h

Index: extensions/browser/api/cast_channel/cast_test_util.h
diff --git a/extensions/browser/api/cast_channel/cast_test_util.h b/extensions/browser/api/cast_channel/cast_test_util.h
index f70af01ff3e21eb66273a160d6304871e9bfe9b9..c01cf64b045c6db17609e8661dab365e2ebdaf8f 100644
--- a/extensions/browser/api/cast_channel/cast_test_util.h
+++ b/extensions/browser/api/cast_channel/cast_test_util.h
@@ -92,9 +92,12 @@ class MockCastSocket : public CastSocket {
 
   MockCastTransport* mock_transport() const { return mock_transport_.get(); }
 
+  const std::string& owner_extension_id() const override;
+
  private:
   std::unique_ptr<MockCastTransport> mock_transport_;
   std::unique_ptr<CastTransport::Delegate> delegate_;
+  std::string owner_extension_id_;
 
   DISALLOW_COPY_AND_ASSIGN(MockCastSocket);
 };