Linux: fix build with system libevent.

message_pump_libevent_unittest.cc uses libevent directly, and it must get USE_SYSTEM_LIBEVENT symbol to work correctly with libevent. To make that work, base_unittests must depend on libevent.gyp, which uses direct_dependent_settings to set USE_SYSTEM_LIBEVENT.

This is upstreaming a Gentoo Linux patch.

BUG=none

Review URL: http://codereview.chromium.org/7578011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@95519 0039d316-1c4b-4281-b951-d872f2087c98

base/base.gyp

@@ -283,6 +283,9 @@
             'message_pump_libevent_unittest.cc',
           ],
         }, {  # OS != "win"
+          'dependencies': [
+            '../third_party/libevent/libevent.gyp:libevent'
+          ],
           'sources/': [
             ['exclude', '^win/'],
           ],