* Electron Version: 3.0.0-beta.3
* Operating System Ubuntu 18.04
* Last known working Electron version: none  ... still fails on 2.0.5

**Expected Behavior**

Font Subpixel AA should work... only works when rendering a .HTML file, not via BrowserWindow.

**Actual behavior**

Subpixel AA only works when I load a .html file.. not a .js file.

**To Reproduce**

https://github.com/burtonator/electron3-fuzzy-text

Here is a repo.

This works:

```
./node_modules/.bin/electron test.html
```

This will fail:

```
./node_modules/.bin/electron index.js
```
The only way to actually see that it's failing is to use a zoom tool like ```kmag```

**Screenshots**

Here's loading the .html file on the command line. Notice the AA is working by the orange color on the outside of the text:

![image](https://user-images.githubusercontent.com/45447/43037663-8731acd2-8cc4-11e8-99bf-f2adfbfdecc4.png)

Here is the SAME text and same test.html file but I loaded it via BrowserWindow in my index.js script.

![image](https://user-images.githubusercontent.com/45447/43037676-a22fa30e-8cc4-11e8-8bee-4d20bdfde57f.png)

Electron fails to use AA text rendering in the new window.  

Hopefully this might help track down the bug.  


atom/browser/web_contents_preferences.cc
command_line->AppendSwitchASCII(::switches::kEnableBlinkFeatures, s);
  
  if (GetAsString(&preference_, options::kDisableBlinkFeatures, &s))
    command_line->AppendSwitchASCII(::switches::kDisableBlinkFeatures, s);
  if (guest_instance_id) {
    
    
    auto* manager = WebViewManager::GetWebViewManager(web_contents_);
    if (manager) {
      auto* embedder = manager->GetEmbedder(guest_instance_id);
      if (embedder) {
        auto* relay = NativeWindowRelay::FromWebContents(embedder);
        if (relay) {
          auto* window = relay->window.get();
          if (window) {
            const bool visible = window->IsVisible() && !window->IsMinimized();
            if (!visible) {
              command_line->AppendSwitch(switches::kHiddenPage);
            }
          }
        }
      }
    }
  }
  
  
  
  last_preference_ = preference_.Clone();
}
void WebContentsPreferences::OverrideWebkitPrefs(