Make the Pepper audio delegate properly use the I/O thread for manipulating the audio message filter's delegates.
Make the Pepper audio delegate properly use the I/O thread for manipulating the
audio message filter's delegates.

This required moving the start and stop commands to the I/O thread as well
since now the routing_id is only available on the I/O thread.

BUG=75495
Review URL: http://codereview.chromium.org/6694002

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@78163 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser