increase Builder's prealloc size after colorspace change

BUG=skia:

Change-Id: I003dcbde7d987404ae823df6621e13664cf440a1
Reviewed-on: https://skia-review.googlesource.com/9523
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed