Bug 258558

There are two APIs to create a `WKWebView`: - `PlatformWebView(WKPageConfigurationRef configuration)` - `PlatformWebView(WKContextRef contextRef, WKPageGroupRef pageGroupRef)` If we want to set some preferences, it's quite straightforward using `WKPageConfigurationRef`: ``` auto configuration = adoptWK(WKPageConfigurationCreate()); auto preferences = adoptWK(WKPreferencesCreate()); WKPageConfigurationSetPreferences(configuration.get(), preferences.get()); ``` When using the context and the page group, we don't have access to the configuration object. But it's possible to set preferences to the page group: ``` WKRetainPtr<WKPageGroupRef> pageGroup = adoptWK(WKPageGroupCreateWithIdentifier(Util::toWK("GetUserMedia").get())); WKPreferencesRef preferences = WKPageGroupGetPreferences(pageGroup.get()); ``` When we then create an instance of `WKWebView` we copy `WKPageConfigruation` into `WKWebViewConfigruation` and pass them as a parameter: ``` auto configuration = adoptNS([WKWebViewConfiguration new]); if (auto* preferences = WKPageConfigurationGetPreferences(pageConfiguration)) configuration.get().preferences = (WKPreferences *)preferences; m_view = [[wkViewSubclass alloc] initWithFrame:rect configuration:configuration.get()]; ``` But we ignore pageGroup's preferences. I must say, that it's really confusing to have two levels of `Preferences`: WKPageConfiguration |-WKPreferences |-WKPageGroup |-WKPreferences but for now, we should at least copy pageGroup's preferences to WebViewConfiguration.