* Output of `node_modules/.bin/electron --version`: v3.0.2
* Operating System (Platform and Version): Windows 10 Pro 17134
* Output of `node_modules/.bin/electron --version` on last known working Electron version (if applicable): v1.6.15

**Expected Behavior**
Reloading (Ctrl R) a `BrowserWindow` with `backgroundColor` set should display that background color until the page begins to load.

**Actual behavior**
Reloading (Ctrl R) a `BrowserWindow` with `backgroundColor` set displays white until the page begins to load.

**To Reproduce**
I've reproduced the issue in electron-quick-start by:
* Adding ` style="background-color: transparent;"` to `index.html`'s `body` tag (pedantic, I know)
* Adding `backgroundColor: '#ffff0000', ` to `main.js`'s `BrowserWindow` options
* Alternatively, clone my fork of electron-quick-start:
```sh
$ git clone https://github.com/adill/electron-quick-start.git -b background-color-reload
$ npm install
$ npm start
```
1. Notice the red background color on the page (transparent body is showing through to the opaque red background.)
2. Reload (Ctrl R)
3. Notice the background color is now white

atom/renderer/renderer_client_base.cc
const PreferencesManager* preferences_manager,
    v8::Isolate* isolate) {
  if (preferences_manager->preferences())
    return mate::ConvertToV8(isolate, *preferences_manager->preferences());
  else
    return v8::Null(isolate);
}
std::vector<std::string> ParseSchemesCLISwitch(base::CommandLine* command_line,
                                               const char* switch_name) {
  std::string custom_schemes = command_line->GetSwitchValueASCII(switch_name);
  return base::SplitString(custom_schemes, ",", base::TRIM_WHITESPACE,
                           base::SPLIT_WANT_NONEMPTY);
}
void SetHiddenValue(v8::Handle<v8::Context> context,