From bug 251903, comment 48: " I think we should set "middlemouse.paste" to false by default on Android, especially if it helps get this test working. Unlike X11, Android does not use middle mouse button to paste as a standard platform behavior. " This pref is set to true, 2 times, in all.js: http://mxr.mozilla.org/mozilla-central/source/modules/libpref/src/init/all.js#3192 http://mxr.mozilla.org/mozilla-central/source/modules/libpref/src/init/all.js#3458 One of them can be removed, the one that makes the middlemouse.paste pref set to false on Android. Note that this may make dom/tests/mochitest/general/test_paste_selection.html fail on Android, so this has to be made sure then, that test is updated.

From bug 251903, comment 50: " > Actually, by setting this pref to false, it might make the > test_paste_selection.html test fail. I filed bug 1046398 for setting the > "middlemouse.paste" pref to false. It won't fail but currently Android is the only place the middlemouse.paste pref gets tested when there is only one clipboard. " So it won't cause a failure in that test, but will reduce a testing path. It seems to me that a solution for that would be, to test these kinds of platform-specific preferences in a separate test file and then we could just use test_paste_selection.html for tests in the case of middlemouse.paste=false and in the case of middlemouse.paste=true.

We flipped this pref in bug 366945.