Change the root url based on the initial channel query parameter (#2014)
Change the root url based on the initial channel query parameter (#2014)

call _handleChannelSwitched when channels menu component is initialized

This makes sure that the root url in DartservicesApi is set to the
initial value of the query parameter
dart-lang/dart-pad,dart-lang/dart-pad,dart-lang/dart-pad,dart-lang/dart-pad