[MediaRouter] Adds GetPresentationServiceDelegate impl to ChromeContentBrowserClient

chrome/browser/media/router/presentation_service_delegate_impl.cc

Index: chrome/browser/media/router/presentation_service_delegate_impl.cc
diff --git a/chrome/browser/media/router/presentation_service_delegate_impl.cc b/chrome/browser/media/router/presentation_service_delegate_impl.cc
index ebe434d4e8e8d01fd6607d8d7a32a5e352b74e62..30b1c8a7766b5c88d4aa6a196001e9f3726902ca 100644
--- a/chrome/browser/media/router/presentation_service_delegate_impl.cc
+++ b/chrome/browser/media/router/presentation_service_delegate_impl.cc
@@ -327,6 +327,15 @@ void PresentationFrameManager::SetMediaRouterForTest(MediaRouter* router) {
   router_ = router;
 }
 
+PresentationServiceDelegateImpl*
+PresentationServiceDelegateImpl::GetOrCreateForWebContents(
+    content::WebContents* web_contents) {
+  DCHECK(web_contents);
+  // CreateForWebContents does nothing if the delegate instance already exists.
+  PresentationServiceDelegateImpl::CreateForWebContents(web_contents);
+  return PresentationServiceDelegateImpl::FromWebContents(web_contents);
+}
+
 PresentationServiceDelegateImpl::PresentationServiceDelegateImpl(
     content::WebContents* web_contents)
     : web_contents_(web_contents),