fix($mdInteraction): clean up events on $rootScope destroy

[codymikol]

this prevents unit tests from leaking memory

Fixes: #11493

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PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Enhancement
[ ] Documentation content changes
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
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What is the current behavior?

Currently the $mdInteraction service registers when invoked. This causes a memory leak in unit tests because nothing is in place to clean up the events.

Issue Number: #11493

What is the new behavior?

Now on the $destroy event of rootScope the events registered will be unregistered.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[codymikol]

I have another version that squishes the init and deregister methods into one that is passed 'on' or 'off', but thought this might be overly clever and less easily understood. It does have the have the benefit of having one place where events are manipulated so you don't have to worry about keeping both the init and deregister methods in sync. Let me know if that is preferred. 🐔

[Splaktar]

This is great! Thank you!

Is there any way to verify this fix in a unit test? Maybe destroy the the rootScope and then check if the handlers are still there?

[Splaktar]

In the commit message, can you please change Fixes: #11493 to Fixes #11493?

[codymikol]

In the commit message, can you please change Fixes: #11493 to Fixes #11493?

Changed 🐔

This is great! Thank you!

Is there any way to verify this fix in a unit test? Maybe destroy the the rootScope and then check if the handlers are still there?

I added unit tests that see if the lastInteractionType is modified after an event is fired. 🐔

[Splaktar]

LGTM