What breed is this dog?

about a month ago i was on my break at work,i work at the safeway supermarket in stockton,ca.im part of the night crew & we eat prepared foods that didnt get sold that day..ppl complain about smokers so i take my breaks behind the store where the dumpster is at,that day i got some roast beef with potatoes & green beans & i headed behind the store & i found a skinny black dog trying to eat out of the trash..this dog looked like it was starving so i gave him my plate of roast beef,this dog ate the food + the paper plate & he started licking my hand after that,i instantly became attached to this dog and i took him home..with a steady diet this dog gained some weight & filled out..he is a very active dog & likes to play...i named him shadow,but i want to know what breed he might be...here are a few pics of shadow hopefully someone can guess what breed he is http://i440.photobucket.com/albums/qq124/rogulo/pic101308_2.jpg http://i440.photobucket.com/albums/qq124/rogulo/pic101308_4.jpg