Stop handling NULL source in views::View::ConvertPointToTarget() and views::View::ConvertRectToTarget().

The reason for the CL is that the current code to handle a NULL source in views::View is wrong when the target has a rotation or a scale transform.

BUG=None
TEST=None
R=sadrul@chromium.org, sky@chromium.org, xiyuan@chromium.org

Review URL: https://codereview.chromium.org/71133002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239341 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 239341