Thanks for filing. I believe some of these differences might be expected due to how Gecko handles HCM in the browser chrome vs. content. I'm taking a closer look to verify.
Bug 2069260 Comment 3 Edit History
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Thanks for filing. I believe some of these differences might be expected due to how Gecko handles HCM in the browser chrome vs. content. I'm taking a closer look to verify and fix what might genuinely be broken.