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* Electron version: 1.7.2
* Operating system: macOS Sierra

### Expected behavior

Webview appear

### Actual behavior

It don't

### How to reproduce

1. Create a browser window with contextIsolation on true and webviewTag on true
2. Inside of it, add a webview
3. Run it, webview should not appear

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atom/renderer/renderer_client_base.h
v8::Local<v8::String> source);
 protected:
  void AddRenderBindings(v8::Isolate* isolate,
                         v8::Local<v8::Object> binding_object);
  
  void RenderThreadStarted() override;
  void RenderFrameCreated(content::RenderFrame*) override;
  void RenderViewCreated(content::RenderView*) override;
  std::unique_ptr<blink::WebSpeechSynthesizer> OverrideSpeechSynthesizer(
      blink::WebSpeechSynthesizerClient* client) override;
  bool OverrideCreatePlugin(content::RenderFrame* render_frame,
                            const blink::WebPluginParams& params,
                            blink::WebPlugin** plugin) override;
  void AddSupportedKeySystems(
      std::vector<std::unique_ptr<::media::KeySystemProperties>>* key_systems)
      override;
  bool IsKeySystemsUpdateNeeded() override;
 private:
  std::unique_ptr<PreferencesManager> preferences_manager_;
#if defined(WIDEVINE_CDM_AVAILABLE)
  ChromeKeySystemsProvider key_systems_provider_;
#endif
  bool isolated_world_;
  std::string renderer_client_id_;
  
  int64_t next_context_id_ = 0;
};
}  
#endif