In medium bowl, mix tomato topping ingredients. Cover; refrigerate until serving time.
Between pieces of plastic wrap or waxed paper, place each chicken breast smooth side down; gently pound with flat side of meat mallet or rolling pin until 1/4 inch thick. Sprinkle chicken with garlic salt and 1/8 teaspoon pepper.
In shallow bowl, beat egg and milk with fork until blended. Spread flour on shallow plate. Spread bread crumbs on another shallow plate. Coat chicken with flour, then dip into egg mixture and coat with bread crumbs.
In 12-inch nonstick skillet, heat 2 tablespoons oil over medium-high heat. Reduce heat to medium. Add chicken; cook 10 to 15 minutes, turning once, until crumbs are golden brown and chicken is no longer pink in center. Serve tomato topping over chicken.