Fix slider appearance and support zoom on Mac

Slider appearance had some issues:
- Track didn't have rounded corners
- Thumb was upside down
- Thumb and track weren't aligned
- Slider didn't zoom

This patch fixes them by drawing the slider with GraphicsContext instead of using NSSliderCell. This means the slider appearance on Snow Leopard will change to the Lion one, but it fixes so many issues that its worth it.

Test=Tested by existing range-appearance-* tests.
BUG=130259

Review URL: https://chromiumcodereview.appspot.com/16455007

git-svn-id: svn://svn.chromium.org/blink/trunk@153073 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Don't force layout for offsetWidth of fixed width elements.

This improves page load time of The Economist by 41% (3.4s -> 2.0s) on
my z620 workstation.

I believe the change in the inspector/styles/device-metrics-fit-window.html expectations is a progression.
The div being measured has a fixed width of 1024 and there is a zoom on the page.
It looks to me like there was a rounding error previously.

BUG=247470
R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/17571004

git-svn-id: svn://svn.chromium.org/blink/trunk@153074 bbb929c8-8fbe-4397-9dbb-9b2b20218538