FORT WORTH, Texas — For three quarters, No. 7 TCU looked firmly on the verge of being upset by in-state rival Texas Tech as the Horned Frogs trailed 17-13 entering the fourth quarter. One of the best offenses in the country was without its top player in star receiver Quentin Johnston and was out of sorts against an aggressive Texas Tech defense that was playing above itself. Then the fourth quarter happened. The Horned Frogs scored 21 straight points in the final quarter to alleviate all the built-up stress in Amon G. Carter Stadium. TCU moved to 9-0 with a 34-24 win over its in-state rivals. …