Use GetXDisplay() instead of XOpenDisplay() in IdleQueryLinux.
Use GetXDisplay() instead of XOpenDisplay() in IdleQueryLinux.

We weren't checking that XOpenDisplay was actually succeeding before
attempting to use the display.

BUG=82308
TEST=none

Review URL: http://codereview.chromium.org/7015007

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@85138 0039d316-1c4b-4281-b951-d872f2087c98

yitian134/chromium,yitian134/chromium,ropik/chromium,adobe/chromium,gavinp/chromium,adobe/chromium,gavinp/chromium,yitian134/chromium,yitian134/chromium,adobe/chromium,gavinp/chromium,yitian134/chromium,adobe/chromium,ropik/chromium,ropik/chromium,ropik/chromium,ropik/chromium,gavinp/chromium,adobe/chromium,yitian134/chromium,ropik/chromium,gavinp/chromium,adobe/chromium,ropik/chromium,yitian134/chromium,adobe/chromium,ropik/chromium,gavinp/chromium,adobe/chromium,adobe/chromium,adobe/chromium,gavinp/chromium,ropik/chromium,gavinp/chromium,yitian134/chromium,gavinp/chromium,yitian134/chromium,adobe/chromium,yitian134/chromium,gavinp/chromium