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### Issue Details

* **Electron Version:**
  * Tested with 8.0.0 and v9.0.0-beta.1
* **Operating System:**
  * macOS 10.15.3 (19D76)
* **Last Known Working Electron version:**
  * 7.1.12

### Expected Behavior

`navigator.mediaDevices.enumerateDevices()` should return a list of MediaDevices with a `label` and a `deviceId` property. The `deviceId` property should stay the same across reloads and restarts.

### Actual Behavior
The `deviceId` property changes with every reload/restart.

### To Reproduce
Simply execute `navigator.mediaDevices.enumerateDevices()` in the renderer process and compare the ids of the media devices to a different execution.

See this fork for an example:
https://github.com/codedrift/electron-quick-start

```sh
$ git clone https://github.com/codedrift/electron-quick-start -b media-device-ids
$ npm install
$ npm start || electron .
```

### Additional Information
It seems to work fine in a regular Chrome 80 browser. 

shell/browser/electron_browser_client.h
const GURL& effective_url) override;
  
  void RenderProcessHostDestroyed(content::RenderProcessHost* host) override;
  void RenderProcessReady(content::RenderProcessHost* host) override;
  void RenderProcessExited(
      content::RenderProcessHost* host,
      const content::ChildProcessTerminationInfo& info) override;
 private:
  struct ProcessPreferences {
    bool sandbox = false;
    bool native_window_open = false;
    bool disable_popups = false;
    bool web_security = true;
    content::BrowserContext* browser_context = nullptr;
  };
  bool ShouldForceNewSiteInstance(content::RenderFrameHost* current_rfh,
                                  content::RenderFrameHost* speculative_rfh,
                                  content::BrowserContext* browser_context,
                                  const GURL& dest_url,
                                  bool has_request_started) const;
  bool NavigationWasRedirectedCrossSite(
      content::BrowserContext* browser_context,
      content::SiteInstance* current_instance,
      content::SiteInstance* speculative_instance,
      const GURL& dest_url,
      bool has_request_started) const;
  void AddProcessPreferences(int process_id, ProcessPreferences prefs);
  void RemoveProcessPreferences(int process_id);
  bool IsProcessObserved(int process_id) const;
  bool IsRendererSandboxed(int process_id) const;