More attempts at clipping perf.

With the 1.5x allocation strategy, it can take more reallocations
to reach a similar size as before. Increasing this initial size
reduces the number of reallocations. 

Also reduce size of Geometry struct slightly.

Bug: skia:7230
Change-Id: Ied3f275b01b07aa300e0b7e1f24abc5fc3853ea7
Reviewed-on: https://skia-review.googlesource.com/64500
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
4 files changed