[turbofan] Small fixes to PipelineStatistics. Collect statistics in tests.

[turbofan] Small fixes to PipelineStatistics. Collect statistics in tests.

R=bmeurer@chromium.org
BUG=

Committed: https://crrev.com/9833844268357590243732a53e2a7fc0dc5fcc9e
Cr-Commit-Position: refs/heads/master@{#28192}

[Benedikt Meurer, 2015-05-04 10:53:46]

lgtm

[titzer, 2015-05-04 11:03:44]

The CQ bit was checked by titzer@chromium.org

[commit-bot: I haz the power, 2015-05-04 11:03:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1122753002/1

[commit-bot: I haz the power, 2015-05-04 11:05:50]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-04 11:05:57]

Patchset 1 (id:??) landed as
https://crrev.com/9833844268357590243732a53e2a7fc0dc5fcc9e
Cr-Commit-Position: refs/heads/master@{#28192}

[Michael Achenbach, 2015-05-04 15:36:06]

machenbach@chromium.org changed reviewers:
+ machenbach@chromium.org

[Michael Achenbach, 2015-05-04 15:36:07]

[Sheriff] Speculative revert for breaking arm64 nosnap:
http://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20arm64%20-%20s...

[Michael Achenbach, 2015-05-04 15:38:42]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/1119963003/ by machenbach@chromium.org.

The reason for reverting is: [Sheriff] Speculative revert for breaking arm64
nosnap:
http://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20arm64%20-%20s....