When CheckDeviceStats returns S_PRESENT_MODE_CHANGED, reset display mode and retest for device lost.

Unless the display mode is reset, CheckDeviceLost can keep returning S_PRESENT_MODE_CHANGED, potentially masking a device lost on account of a GPU hang, causing ANGLE to fail to report context lost.
Review URL: https://codereview.appspot.com/7381061

git-svn-id: https://angleproject.googlecode.com/svn/trunk@1986 736b8ea6-26fd-11df-bfd4-992fa37f6226