This block was supposed to be landed as part of r242725.

I described it in my correspondence on
https://codereview.chromium.org/119713002/ , but somehow failed to actually put
it into the patch.

BUG=none
TEST=Extension infobars should actually reserve 6 px + the extension-controlled height
TBR=msw

Review URL: https://codereview.chromium.org/122503002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242729 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242729