Speed improvements to SubstringSetMatcher

Speed improvements to SubstringSetMatcher

This is an attempt to reland https://codereview.chromium.org/14780003/ which was reverted as https://codereview.chromium.org/15045002/.
Patch set 1 here is identical with p.s. 7 in https://codereview.chromium.org/14780003/. The failing buildbot was linux compile (dbg), so trying it here explicitly.

Original description:

The main one is coputing the Aho-Corasick tree size in advance.

Also contained are code clean-ups and minor optimisations, like removing HasEdge/GetEdge sequences, or adding const to aid compiler optimisations.

This was tested on a benchmark adding 20k+ patterns. It showed a reduction of the running time by 30%.

BUG=236368
TBR=battre

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=198871

[vabr (Chromium), 2013-05-08 09:32:14]

Hi Dominic,
I'm going to TBR you on this, as it is a trivial change from what you already
approved of in https://codereview.chromium.org/14780003/.

It's funny, obviously the compiler (GCC?) on the linux debug trybot had problems
with kNoSuchEdge being defined in the header file. I could not reproduce that
with clank on my linux box.

I put the definition to the cc file, and the trybot complains no more, so going
to commit that.

Vaclav

[vabr (Chromium), 2013-05-08 10:06:49]

Committed patchset #2 manually as r198871 (presubmit successful).