[Mac] Do not use |+[NSColor selectedMenuItemColor]| in a gradient due to color space issues.

BUG=49448
TEST=On both 10.5 and 10.6, open the Wrench menu and click a button. Button has blue gradient.

Review URL: http://codereview.chromium.org/3046052

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@55327 0039d316-1c4b-4281-b951-d872f2087c98
1 file changed