* 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
#include "atom/browser/web_contents_preferences.h"
#include <algorithm>
#include <string>
#include <utility>
#include <vector>
#include "atom/browser/native_window.h"
#include "atom/browser/web_view_manager.h"
#include "atom/common/native_mate_converters/value_converter.h"
#include "atom/common/options_switches.h"
#include "base/command_line.h"
#include "base/memory/ptr_util.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/utf_string_conversions.h"
#include "cc/base/switches.h"
#include "content/public/browser/render_frame_host.h"
#include "content/public/browser/render_process_host.h"
#include "content/public/common/content_switches.h"
#include "content/public/common/web_preferences.h"
#include "native_mate/dictionary.h"
#include "net/base/filename_util.h"
#if defined(OS_WIN)
#include "ui/gfx/switches.h"
#endif
DEFINE_WEB_CONTENTS_USER_DATA_KEY(atom::WebContentsPreferences);
namespace {
bool GetAsString(const base::Value* val,