[MediaRouter] PresentationServiceDelegateImpl cleanup.

content/browser/presentation/presentation_service_impl.cc

Index: content/browser/presentation/presentation_service_impl.cc
diff --git a/content/browser/presentation/presentation_service_impl.cc b/content/browser/presentation/presentation_service_impl.cc
index 6fb5641c60ac183f86feb0a642f0f09151575f0d..50d561113634adb8533b0c70bfa4608286dd6d2b 100644
--- a/content/browser/presentation/presentation_service_impl.cc
+++ b/content/browser/presentation/presentation_service_impl.cc
@@ -123,7 +123,7 @@ void PresentationServiceImpl::SetClient(
 
 void PresentationServiceImpl::ListenForScreenAvailability(const GURL& url) {
   DVLOG(2) << "ListenForScreenAvailability " << url.spec();
-  if (!controller_delegate_) {
+  if (!controller_delegate_ || !url.is_valid()) {
     client_->OnScreenAvailabilityUpdated(
         url, blink::mojom::ScreenAvailability::UNAVAILABLE);
     return;
@@ -459,13 +459,13 @@ PresentationServiceImpl::ScreenAvailabilityListenerImpl::
     ScreenAvailabilityListenerImpl(const GURL& availability_url,
                                    PresentationServiceImpl* service)
     : availability_url_(availability_url), service_(service) {
+  DCHECK(availability_url_.is_valid());
   DCHECK(service_);
   DCHECK(service_->client_.get());
 }
 
 PresentationServiceImpl::ScreenAvailabilityListenerImpl::
-~ScreenAvailabilityListenerImpl() {
-}
+    ~ScreenAvailabilityListenerImpl() = default;
 
 GURL PresentationServiceImpl::ScreenAvailabilityListenerImpl::
     GetAvailabilityUrl() const {