[DevTools] Emulate UA stylesheet as a part of device emulation.

BUG=320278

Review URL: https://codereview.chromium.org/104453002

git-svn-id: svn://svn.chromium.org/blink/trunk@163257 bbb929c8-8fbe-4397-9dbb-9b2b20218538
'media/video-frame-accurate-seek.html' is super flaky.

'media/video-frame-accurate-seek.html' is flaky on all platforms, but particularly on Windows, where it's practically indistinguishable from a failing test.

http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=media%2Fvideo-frame-accurate-seek.html

BUG=326139
TBR=scherkus@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/106363005

git-svn-id: svn://svn.chromium.org/blink/trunk@163258 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Inline ProfileType.createProfile method

The method is only called by corresponding profile types so I just inlined profile construction and removed createProfile method from the base class.

BUG=324769
R=loislo@chromium.org

Review URL: https://codereview.chromium.org/99623005

git-svn-id: svn://svn.chromium.org/blink/trunk@163259 bbb929c8-8fbe-4397-9dbb-9b2b20218538