This patch covers multiple cases:
- Pre-existing issue: adoptTabGroup adopts tabs by first moving the tabs
elsewhere, then moving it into a group. When moved into a group,
TabMove is fired, which previously translated to tabs.onMoved. That
would result in too much event noise.
- When tabGroups.move is called, it first adopted the tab group in
another window, and then moved the tab group as a whole. This
results in unnecessary tabs.onMoved events too. The fix is to specify
the desired position at once to adoptTabGroup.
Differential Revision: https://phabricator.services.mozilla.com/D246701
6899ed5a68