Implemented VLOG() et al.

Implemented VLOG(), VLOG_IF(), VLOG_IS_ON().  Added --v and --vmodule
switches.

Changed some spammy sync-related logs to use VLOG.

BUG=56965
TEST=New unittests

Review URL: http://codereview.chromium.org/3448028

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@60976 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/base/base.gyp b/base/base.gyp
index 5ab2928..3655bda 100644
--- a/base/base.gyp
+++ b/base/base.gyp
@@ -161,6 +161,7 @@
         'utf_string_conversions_unittest.cc',
         'values_unittest.cc',
         'version_unittest.cc',
+        'vlog_unittest.cc',
         'waitable_event_unittest.cc',
         'waitable_event_watcher_unittest.cc',
         'watchdog_unittest.cc',