Bug 987461: prevent bookmark menu button dropmarker icon to stretch when placed in certain toolbars. r=Gijs, a=sylvestre

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extra : transplant_source : o%07%08%ED%20%03%98%19s%F2d%F7%09%E5z%8B%19%7E1.
Bug 957151: fix styling of primary toolbar buttons on the bookmarks toolbar on Linux. r=Gijs, a=sylvestre

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extra : transplant_source : r%23c%D6i%98%25%E2%D2%EE9%08DoP%2A%08%EE%B7g