"Unpause" command opens Spotify tab when on a text to speech mode tab

[alexandra-martin]

Prerequisites:

Mic permissions are enabled.
Have an opened active tab supporting text to speech mode which is not reading, e.g. a New York Times article.

STR:

1. Use the shortcut or click on the mic icon from the browser toolbar.
2. Say or write an "Unpause" command.

Expected result:

Reader starts reading.

Actual result:

Spotify opens in a new tab.

Notes:

Reproduced on Mac 10.14.6 and Win10x64 with Firefox Nightly 71.0a1 (64-bit).
When the Spotify tab opens and it is selected it intermittently plays or not the song that was last played in a previous session.

[alexandra-martin]

Verified on Mac 10.14.6 and Win10x64 with Firefox Nightly 71.0a1 (64-bit).
On Mac the "Unpause" command is working as intended.
On Win the "Unpause" is not opening the Spotify tab anymore, but it also doesn't work to resume the narration, as described in 330.