cc: Fix the DCHECK in PictureLayer::PushPropertiesTo

If the pile has been resized to be empty the DCHECK does not hold, so we only DCHECK when pile doesn't get resized.

BUG=276988

Review URL: https://codereview.chromium.org/37923003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230664 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230664