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 08f0b3a7dc12111e38939dbca34fefad8b9ac24f..a83c3acee17ddc656259fc59788e899187390977 100644
--- a/ios/public/provider/chrome/browser/chrome_browser_provider.mm
+++ b/ios/public/provider/chrome/browser/chrome_browser_provider.mm
@@ -102,6 +102,12 @@ UITextField<TextFieldStyling>* ChromeBrowserProvider::CreateStyledTextField(
   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;