Set the expected number of initializers to 2 on the Mac.

This was broken for a very long time and the initializers regressed.
There was a tool to update the perf_expectations.json file, but it
is either broken or has zero documentation. The perf team disavows
it. This is unmaintained, so I'm manually hacking this file to get
it to a state in which it works.

BUG=831951, 832854
NOTRY=true
NOPRESUBMIT=true
TBR=thakis@chromium.org

Change-Id: Idf1bd61d40540d0b85497e6669297fb54c2c2a28
Reviewed-on: https://chromium-review.googlesource.com/1012743
Commit-Queue: Avi Drissman <avi@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550723}

tools/perf_expectations/perf_expectations.json

@@ -4,6 +4,6 @@
  "linux-release/sizes/chrome-si/initializers": {"reva": 480969, "revb": 480969, "type": "absolute", "better": "lower", "improve": 9, "regress": 9, "tolerance": 0, "sha1": "b639bbc4"},
  "linux-release/sizes/nacl_helper-si/initializers": {"reva": 480969, "revb": 480969, "type": "absolute", "better": "lower", "improve": 7, "regress": 9, "sha1": "3394be7f"},
  "linux-release/sizes/nacl_helper_bootstrap-si/initializers": {"reva": 114822, "revb": 115019, "type": "absolute", "better": "lower", "improve": 0, "regress": 0, "sha1": "dd908f29"},
- "mac-release/sizes/chrome-si/initializers": {"reva": 281731, "revb": 281731, "type": "absolute", "better": "lower", "improve": 0, "regress": 0, "tolerance": 0, "sha1": "01759b7f"},
+ "mac-release/sizes/chrome-si/initializers": {"reva": 281731, "revb": 281731, "type": "absolute", "better": "lower", "improve": 0, "regress": 2, "tolerance": 0, "sha1": "01759b7f"},
  "load": true
 }