Some issues (such as "Failed to cast, please try again") become irrelevant when the next cast attempt succeeds, but don't disappear until the user manually dismisses the issue banner. When this happens, the toolbar icon would be in the warning/error state even if there is nothing wrong with the current session. These issues should disappear on their own at this point.

We can implement this once Derek's redesign for issues [1] lands. We can add a boolean attribute to IssueInfo for whether the issue should disappear automatically.

[1] https://codereview.chromium.org/2176613003/