Commits on Aug 25, 2017

1. Use Parser::skip_whitespace in a few places to make Parser::try rewin… …

   …d less.
   
   Gecko’s CSS parsing microbenchmarks before:
   
   ```
     43.437 ±  0.391 ms    Stylo.Servo_StyleSheet_FromUTF8Bytes_Bench
     29.244 ±  0.042 ms    Stylo.Gecko_nsCSSParser_ParseSheet_Bench
    281.884 ±  0.028 ms    Stylo.Servo_DeclarationBlock_SetPropertyById_Bench
    426.242 ±  0.008 ms    Stylo.Servo_DeclarationBlock_SetPropertyById_WithInitialSpace_Bench
   ```
   
   After:
   
   ```
     29.779 ±  0.254 ms    Stylo.Servo_StyleSheet_FromUTF8Bytes_Bench
     28.841 ±  0.031 ms    Stylo.Gecko_nsCSSParser_ParseSheet_Bench
    296.240 ±  4.744 ms    Stylo.Servo_DeclarationBlock_SetPropertyById_Bench
    293.855 ±  4.304 ms    Stylo.Servo_DeclarationBlock_SetPropertyById_WithInitialSpace_Bench
   ```

   

   SimonSapin committed Aug 25, 2017

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