* 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
SetDefaultBoolIfUndefined(options::kNodeIntegrationInWorker, false);
  SetDefaultBoolIfUndefined(options::kWebviewTag, node);
  SetDefaultBoolIfUndefined(options::kSandbox, false);
  SetDefaultBoolIfUndefined(options::kNativeWindowOpen, false);
  SetDefaultBoolIfUndefined(options::kContextIsolation, false);
  SetDefaultBoolIfUndefined("javascript", true);
  SetDefaultBoolIfUndefined("images", true);
  SetDefaultBoolIfUndefined("textAreasAreResizable", true);
  SetDefaultBoolIfUndefined("webgl", true);
  bool webSecurity = true;
  SetDefaultBoolIfUndefined(options::kWebSecurity, webSecurity);
  
  
  if (web_preferences.Get(options::kWebSecurity, &webSecurity) &&
      !webSecurity) {
    SetDefaultBoolIfUndefined(options::kAllowRunningInsecureContent, true);
  } else {
    SetDefaultBoolIfUndefined(options::kAllowRunningInsecureContent, false);
  }
#if defined(OS_MACOSX)
  SetDefaultBoolIfUndefined(options::kScrollBounce, false);
#endif
  SetDefaultBoolIfUndefined(options::kOffscreen, false);
  last_preference_ = preference_.Clone();
}
WebContentsPreferences::~WebContentsPreferences() {
  instances_.erase(std::remove(instances_.begin(), instances_.end(), this),
                   instances_.end());
}
bool WebContentsPreferences::SetDefaultBoolIfUndefined(