Adds methods for Cast support to ios::ChromeBrowserProvider.

ios/public/provider/chrome/browser/chrome_browser_provider.mm

Index: ios/public/provider/chrome/browser/chrome_browser_provider.mm
diff --git a/ios/public/provider/chrome/browser/chrome_browser_provider.mm b/ios/public/provider/chrome/browser/chrome_browser_provider.mm
index df6ca1f753ca9c84d07935416295b852b5213938..ea6a1fd2077587db09e54fbe90b7750747910582 100644
--- a/ios/public/provider/chrome/browser/chrome_browser_provider.mm
+++ b/ios/public/provider/chrome/browser/chrome_browser_provider.mm
@@ -106,6 +106,12 @@ id<AppRatingPrompt> ChromeBrowserProvider::CreateAppRatingPrompt() const {
   return nil;
 }
 
+void ChromeBrowserProvider::InitializeCastService(id tab_model) const {}
+
+void ChromeBrowserProvider::AddCastAPISupportToWebState(
+    web::WebState* web_state,
+    NSString* tab_id) const {}
+
 bool ChromeBrowserProvider::IsSafeBrowsingEnabled(
     const base::Closure& on_update_callback) {
   return false;