* Output of `node_modules/.bin/electron --version`: v3.0.0-beta.8
* Operating System (Platform and Version): Windows 10 10.0.16299 Build 16299
* Output of `node_modules/.bin/electron --version` on last known working Electron version (if applicable): v2.0.8

**Expected Behavior**
Webview DevTools should open in a window that is properly sized.

**Actual behavior**
Webview DevTools open in window with minimal size and are therefore not visible.

**To Reproduce**
**Edit** Works in BrowserWindow.webContents.openDevTools() Works **not** in webView.openDevTools()

**Screenshots**
![too_small_devtools_window](https://user-images.githubusercontent.com/6893212/44841398-850fed80-ac43-11e8-8bed-849d45473683.png)

**Additional Information**
Only reproducible on Windows 10 10.0.16299 Build 16299. Works correctly on MacOS High Sierra 10.13.4

brightray/browser/inspectable_web_contents_impl.cc
is_guest_(is_guest),
      view_(CreateInspectableContentsView(this)),
      weak_factory_(this) {
  if (is_guest)
    return;
  auto* bounds_dict = pref_service_->GetDictionary(kDevToolsBoundsPref);
  if (bounds_dict) {
    DictionaryToRect(*bounds_dict, &devtools_bounds_);
    
    if (devtools_bounds_.height() < 100 || devtools_bounds_.width() < 100) {
      devtools_bounds_.set_height(600);
      devtools_bounds_.set_width(800);
    }
    if (!IsPointInScreen(devtools_bounds_.origin())) {
      gfx::Rect display;
      if (web_contents->GetNativeView()) {
        display = display::Screen::GetScreen()
                      ->GetDisplayNearestView(web_contents->GetNativeView())
                      .bounds();
      } else {
        display = display::Screen::GetScreen()->GetPrimaryDisplay().bounds();
      }
      devtools_bounds_.set_x(display.x() +
                             (display.width() - devtools_bounds_.width()) / 2);
      devtools_bounds_.set_y(
          display.y() + (display.height() - devtools_bounds_.height()) / 2);
    }
  }
}
InspectableWebContentsImpl::~InspectableWebContentsImpl() {