Chrome Version: 72.0.3610.2
OS: All

What steps will reproduce the problem?
(1) Take a text file and rename it <file>.webm to create an invalid media file.
(2) In the cast dialog, click sources > "Cast file".
(3) Select the invalid file from the file picker.
(4) Select a sink from the device list.

What is the expected result? An error should be displayed regarding the invalid file.

What happens instead? In step 3, the cast icon turns orange, in step 4, it turns blue. In step 4, the first click on the device has no effect other than to return the icon to its blue state. Clicking again casts the current tab.