Handle Javascript-based navigation for iFrame player in WKWebView (#425)

The web iFrame embedded player may use Javascript to open URLs for some UI elements. WKWebView ignores this navigation by default, so this change adds the logic to link to the YT app.

Author: Eric Vargas

Classes/YTPlayerView.m

@@ -62,7 +62,7 @@
 NSString static *const kYTPlayerStaticProxyRegexPattern = @"^https://content.googleapis.com/static/proxy.html(.*)$";
 NSString static *const kYTPlayerSyndicationRegexPattern = @"^https://tpc.googlesyndication.com/sodar/(.*).html$";
 
-@interface YTPlayerView() <WKNavigationDelegate>
+@interface YTPlayerView() <WKNavigationDelegate, WKUIDelegate>
 
 @property (nonatomic) NSURL *originURL;
 @property (nonatomic, weak) UIView *initialLoadingView;
@@ -540,6 +540,20 @@ - (void)webView:(WKWebView *)webView didFailNavigation:(WKNavigation *)navigatio
   }
 }
 
+#pragma mark - WKUIDelegate
+
+- (WKWebView *)webView:(WKWebView *)webView
+createWebViewWithConfiguration:(WKWebViewConfiguration *)configuration
+   forNavigationAction:(WKNavigationAction *)navigationAction
+        windowFeatures:(WKWindowFeatures *)windowFeatures {
+  // Handle navigation actions initiated by Javascript.
+  [[UIApplication sharedApplication] openURL:navigationAction.request.URL
+                                     options:@{}
+                           completionHandler:nil];
+  // Returning nil results in canceling the navigation, which has already been handled above.
+  return nil;
+}
+
 #pragma mark - Private methods
 
 - (NSURL *)originURL {
@@ -770,6 +784,7 @@ - (BOOL)loadWithPlayerParams:(NSDictionary *)additionalPlayerParams {
 
   [self.webView loadHTMLString:embedHTML baseURL: self.originURL];
   self.webView.navigationDelegate = self;
+  self.webView.UIDelegate = self;
 
   if ([self.delegate respondsToSelector:@selector(playerViewPreferredInitialLoadingView:)]) {
     UIView *initialLoadingView = [self.delegate playerViewPreferredInitialLoadingView:self];