Here's the standard procedure:
- Ctrl+A to Select All (MIDI, if any, doesn't need to be included, but it doesn't hurt to select everything).
- Open the Clip tab of the Track Inspector, and expand the Audiosnap section.
- Click to check the 'Enable' box, and give it a moment to finish processing all the tracks.
- Ctrl+A again, and check the box for 'Follow Project Tempo'.
- Change the tempo from 135 to 115.
- Record your part, and then select it and enable 'Follow Project' on that clip as above.
- Change the tempo back to 135, and disable Audiosnap on the original tracks (or not; they'll sound the same either way).
- Bounce to clip(s) the new clip with the appropriate algorithm for the material selected in the Audiosnap palette to get best possible rendered audio quality.
There will be audible degradation; whether it's acceptable or not depends on the material, how it sits in the mix, and your sensitivity to stretching artifacts. Compressing is always easier on the audio then stretching, so it might not be too bad.
You could substitute Noel's suggestion to use Melodyne for the last step of compressing the new audio track to fit the higher tempo, assuming Melodyne's algorithm will sound better than any of the Audiosnap options. If it accepts decimal points for the percentage, you'll want to use 85.2% (.852); 85% is not going to be close enough to give good sync over any significant length of time (it'd be off - too slow - by half a second over a 4-minute song!)
The advantage of the all-Audiosnap procedure is it takes care of the stretching percentage for you in both directions, and the sync will be perfect no matter what tempos you use and whether they produce nice whole-number percentages.