Update a comment to align with the behaviour of the code.

The example of Pass in scoped_ptr<> does not actually compile with either
gcc or clang on Linux. Assuming that this was intended, I've updated the example
comment to be code that would compile.

BUG=none

Review URL: https://codereview.chromium.org/23531052

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227789 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227789