Fix buggy ASSERT in NewDeviceOrientationController.

The assert should test for deviceorientation event instead of devicemotion event.

BUG=

Review URL: https://chromiumcodereview.appspot.com/22144005

git-svn-id: svn://svn.chromium.org/blink/trunk@155610 bbb929c8-8fbe-4397-9dbb-9b2b20218538