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I signed it!

CLAs look good, thanks!

@feichao - lgtm, thx.

Looks rather expensive to evaluate DOM attributes on every Angular tick. MutationObserver would give better performance.

Also, using ng-if instead of ng-show would solve the underlying issue, so a recommendation could be added in the documentation. Another alternative would be to only use the watcher if ng-show or ng-hide are being used.

@clshortfuse any ideas on how to use the watcher only when ng-show or ng-hide are being used?

@feichao can you please add some tests for this?
For example: Verify that the md-mode-indeterminate is applied after the element is displayed via toggling ng-show and verify that the md-mode-indeterminate is removed after the element is hidden via toggling ng-hide.

@Splaktar Sure, you can use a MutationObserver to watch for the ng-show or ng-hide class. If the value exists then a watcher should be created to handle its computed value.

You can see a similar implementation created with md-visible with md-tooltip in #7822

@feichao Thank you very much for your contribution! Can you please update your implementation to only apply the watcher when ng-show or ng-hide are present as described in #10745 (comment)?

Since this whole PR is about performance, it would be best to use this more optimally performing approach.

We'll need to make sure that the MutationObserver has a fallback since we'll need to do something else on IE10.