Show speech button for x-webkit-speech only if the field is editable and focused/hovered.

BUG=325496

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=163860

Review URL: https://codereview.chromium.org/100793006

git-svn-id: svn://svn.chromium.org/blink/trunk@163957 bbb929c8-8fbe-4397-9dbb-9b2b20218538