Cleanup: Remove stale reference to |out_size| from GetScaledContentBitmap's comment.

NOTRY=true

Review URL: https://codereview.chromium.org/182723002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253988 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253988