Fix variable shadowing warning in logging on VS2015

Fix variable shadowing warning in logging on VS2015

d:\src\cr3\src\base\logging.cc(167): error C2220: warning treated as error - no 'object' file generated
d:\src\cr3\src\base\logging.cc(167): warning C4459: declaration of 'log_file' hides global declaration
d:\src\cr3\src\base\logging.cc(103): note: see declaration of 'logging::`anonymous-namespace'::log_file'

There was 3 different things called log_file in this file: a global FileHandle,
a local PathString, and a PathChar* member variable in LoggingSettings. :/

(Should probably rename all the globals to g_ prefixed in a followup.)

R=thakis@chromium.org
BUG=440500
Committed: https://crrev.com/fc5b7077362f170c9205dc976dbd144c6f6bd017
Cr-Commit-Position: refs/heads/master@{#313364}

[scottmg, 2015-01-27 20:26:27]

Patchset #1 (id:1) has been deleted

[Nico, 2015-01-27 20:30:06]

LoG_naMe … aww, no T :-/

lgtm

[scottmg, 2015-01-27 20:30:36]

The CQ bit was checked by scottmg@chromium.org

[commit-bot: I haz the power, 2015-01-27 20:30:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/883853003/40001

[commit-bot: I haz the power, 2015-01-27 21:46:55]

Committed patchset #2 (id:40001)

[commit-bot: I haz the power, 2015-01-27 21:47:51]

Patchset 2 (id:??) landed as
https://crrev.com/fc5b7077362f170c9205dc976dbd144c6f6bd017
Cr-Commit-Position: refs/heads/master@{#313364}