Count up horizontal gap as part of key width

Change-Id: Ic9a070a9b6a461f4c8330d1cc3e2c33fd7369f73

java/src/com/android/inputmethod/keyboard/KeyDetector.java

@@ -135,6 +135,6 @@ public abstract class KeyDetector {
                 mostCommonWidth = width;
             }
         }
-        return mostCommonWidth;
+        return mostCommonWidth + keyboard.getHorizontalGap();
     }
 }