R=go1.11

To fix this, this CL borrows code from the new syntax
package which has a better tuned parser at this point.

Fixes #11377.

Change-Id: Ib9212c945903d6f62abcc59ef5a5767d4ef36981
Reviewed-on: https://go-review.googlesource.com/87495Reviewed-by: Matthew Dempsky <mdempsky@google.com>