improve perf_basic_prof filename reporting

improve perf_basic_prof filename reporting

The buffer used for appending filenames to the string printed to the
perf_basic_prof log was unnecessarily too small. Bump it up to be at least
kUtf8BufferSize.

Truncation of filenames makes it really hard to work with profiles gathered on
Node.js. Because of the way Node.js works, you can have node module dependencies
in deeply nested directories. The last thing you want when investigating a
performance problem is to have script names be truncated.

This patch is a stop-gap. Ideally, I want no truncation of the filename at all
and use a dynamically growing buffer. That would be a larger change, and I
wanted to have a quick fix available that can be back-ported to Node.js LTS
release.

R=yangguo@chromium.org,yurys@chromium.org
BUG=

Committed: https://crrev.com/03ef3cd004c2fd31ae7e48772f106df67b8c2feb
Cr-Commit-Position: refs/heads/master@{#31092}

[ofrobots, 2015-10-02 22:40:29]

On 2015/10/02 22:37:11, ofrobots wrote:

Here's an example of the entries we are currently getting in /tmp/perf*-map:

12a38e14f1a0 45c Function:~
/usr/local/google/home/mattloring/Documents/performance-tests/bookshelf/bookshelf/node_modules/mongodb/node_modules/mongodb-core:1
12a38e14f660 9c
Script:~/usr/local/google/home/mattloring/Documents/performance-tests/bookshelf/bookshelf/node_modules/mongodb/node_modules/mongodb-core

These symbols are not useful at all.

[yurys, 2015-10-02 22:43:47]

lgtm

[Yang, 2015-10-03 03:05:54]

lgtm

[ofrobots, 2015-10-03 05:08:34]

The CQ bit was checked by ofrobots@google.com

[commit-bot: I haz the power, 2015-10-03 05:08:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1388543002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1388543002/1

[commit-bot: I haz the power, 2015-10-03 05:32:51]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-03 05:33:03]

Patchset 1 (id:??) landed as
https://crrev.com/03ef3cd004c2fd31ae7e48772f106df67b8c2feb
Cr-Commit-Position: refs/heads/master@{#31092}

[jrobbins, 2015-10-06 17:34:51]

Test comment.

[Jakob Kummerow, 2015-10-07 09:45:14]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/1390923004/ by jkummerow@chromium.org.

The reason for reverting is: Suspected to cause crbug.com/539892.