[Media Router] Return NotFoundError on dialog exit if appropriate

chrome/browser/ui/webui/media_router/media_router_ui.cc

Index: chrome/browser/ui/webui/media_router/media_router_ui.cc
diff --git a/chrome/browser/ui/webui/media_router/media_router_ui.cc b/chrome/browser/ui/webui/media_router/media_router_ui.cc
index c5572be8d05e283ea506b6bbc59239c35aca9810..882839d990d6a2546ed4411d7dd47a981dc6dffa 100644
--- a/chrome/browser/ui/webui/media_router/media_router_ui.cc
+++ b/chrome/browser/ui/webui/media_router/media_router_ui.cc
@@ -203,11 +203,23 @@ MediaRouterUI::~MediaRouterUI() {
     presentation_service_delegate_->RemoveDefaultPresentationRequestObserver(
         this);
   // If |create_session_request_| still exists, then it means presentation route
-  // request was never attempted.
+  // request was never attempted. This could be because the dialog defaults to

[imcheng, 2016/06/29 17:28:03]

nit: I would just leave out the part about defaulting to mirroring.

[btolsch, 2016/06/30 07:29:16]

Done.

+  // mirroring when no devices support the presentation url.
   if (create_session_request_) {
-    create_session_request_->InvokeErrorCallback(content::PresentationError(
-        content::PRESENTATION_ERROR_SESSION_REQUEST_CANCELLED,
-        "Dialog closed."));
+    bool presentation_sinks_available = std::any_of(
+        sinks_.begin(), sinks_.end(), [](const MediaSinkWithCastModes& sink) {
+          return sink.cast_modes.find(MediaCastMode::DEFAULT) !=

[imcheng, 2016/06/29 17:28:03]

nit: return sink.cast_modes.ContainsValue(MediaCastMode::DEFAULT);

[btolsch, 2016/06/30 07:29:16]

Done.

[imcheng, 2016/06/30 18:24:46]

Thanks. Apologies for suggesting the wrong syntax :)

+                 sink.cast_modes.end();
+        });
+    if (presentation_sinks_available) {
+      create_session_request_->InvokeErrorCallback(content::PresentationError(
+          content::PRESENTATION_ERROR_SESSION_REQUEST_CANCELLED,
+          "Dialog closed."));
+    } else {
+      create_session_request_->InvokeErrorCallback(content::PresentationError(
+          content::PRESENTATION_ERROR_NO_AVAILABLE_SCREENS,
+          "No screens found."));
+    }
   }
 }