Webview offset and height issue on ios when `toolbarposition=top`

When `toolbarposition=top` on ios, the body was covered by the webview at the top, it's the default behavior of this plugin.

Then I found this [pull request](https://github.com/apache/cordova-plugin-inappbrowser/pull/265), change the `rePositionViews` function would sove this problem, but it leads to a new one.

On iphoneX, the webview is out of the screen at the bottom, it seems the webview is 20px higher than it should be.

So, I cut the webview's height, `[self.webView setFrame:CGRectMake(self.webView.frame.origin.x, TOOLBAR_HEIGHT + [self getStatusBarOffset], self.webView.frame.size.width, self.webView.frame.size.height - [self getStatusBarOffset])];`, but it leaves 20px grey area at the bottom, the webview is 20px shorter than it should be.

Could it be `[self.webView setFrame:CGRectMake(self.webView.frame.origin.x, TOOLBAR_HEIGHT + [self getStatusBarOffset], self.webView.frame.size.width, self.webView.frame.size.height - [self getStatusBarOffset] + STATUSBAR_HEIGHT)];`, because the viewbounds height is subtracted by `STATUSBAR_HEIGHT` in `viewWillApear`? It looks pretty good!

Start with the iOS implementation's rePositionViews function and viewWillApear handling, then compare the behavior introduced by pull request 265. Reproduce toolbarposition=top on iOS, including iPhone X, and verify that the webview does not cover the body or leave a bottom gap.

Written by the indexing model from the issue text.