Fix GTK version of options dialog to place it to the center of last active browser window.
Fix GTK version of options dialog to place it to the center of last active browser window.

BUG=1143
TEST=Tested on Linux with two monitors.

Review URL: http://codereview.chromium.org/551094

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@37135 0039d316-1c4b-4281-b951-d872f2087c98

gavinp/chromium,gavinp/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,ropik/chromium,yitian134/chromium,gavinp/chromium,adobe/chromium,adobe/chromium,yitian134/chromium,yitian134/chromium,yitian134/chromium,ropik/chromium,adobe/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,ropik/chromium,gavinp/chromium,gavinp/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,yitian134/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,ropik/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,ropik/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,ropik/chromium,gavinp/chromium,yitian134/chromium,yitian134/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,adobe/chromium,ropik/chromium,adobe/chromium