Revert 163957 "Show speech button for x-webkit-speech only if th..."

The change made browser_tests' SpeechRecognition fail
on at least Linux and Mac.

> 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

TBR=tkent@chromium.org

Review URL: https://codereview.chromium.org/108013005

git-svn-id: svn://svn.chromium.org/blink/trunk@163966 bbb929c8-8fbe-4397-9dbb-9b2b20218538