Created a profile (https://share.firefox.dev/3kQLKJU) and confirmed the slow down is caused by `android.graphics.text.LineBreaker.nComputeLineBreaks`. This is the same problem as originally reported in https://github.com/mozilla-mobile/android-components/issues/5249. I should add that on the device I tested this on (Pixel 3a) it is eventually possible to navigate back or close the tab, but tapping the toolbar does cause a very significant delay, as seen in the profile above. We will look into this again.
Bug 1759951 Comment 24 Edit History
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Created a profile and confirmed the slow down is caused by `android.graphics.text.LineBreaker.nComputeLineBreaks`. This is the same problem as originally reported in https://github.com/mozilla-mobile/android-components/issues/5249. I should add that on the device I tested this on (Pixel 3a) it is eventually possible to navigate back or close the tab, but tapping the toolbar does cause a very significant delay, as seen in the profile above. We will look into this again.