Fix fractured grammar in comment for bug 560234.

js/src/jsemit.h

@@ -314,10 +314,10 @@ struct JSTreeContext {              /* tree context for semantic checks */
 #define TCF_FUN_MODULE_PATTERN 0x200000
 
 /*
- * Flag to prevent a non-escaping function that could be optimized into a null
+ * Flag to prevent a non-escaping function from being optimized into a null
  * closure (i.e., a closure that needs only its global object for free variable
- * resolution, thanks to JSOP_{GET,CALL}UPVAR), because it contains a closure
- * that needs one or more scope objects surrounding this function (i.e., Call
+ * resolution, thanks to JSOP_{GET,CALL}UPVAR), because this function contains
+ * a closure that needs one or more scope objects surrounding it (i.e., Call
  * object for a heavyweight outer function). See bug 560234.
  */
 #define TCF_FUN_ENTRAINS_SCOPES 0x400000