DevTools: Add support for the pseudo :before and :after elements.

R=pfeldman, vsevik
BUG=180291

Review URL: https://chromiumcodereview.appspot.com/21898003

git-svn-id: svn://svn.chromium.org/blink/trunk@158030 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Enable Device Motion API in Blink by default.

We are now ready to enable Device Motion API for
all platforms. This patch sets DeviceMotion status
to stable.

For the corresponding patch to enable Device Motion
API on the Chromium side see:
https://codereview.chromium.org/24220002/

BUG=135804

Review URL: https://chromiumcodereview.appspot.com/23578042

git-svn-id: svn://svn.chromium.org/blink/trunk@158031 bbb929c8-8fbe-4397-9dbb-9b2b20218538