Add libdbus dependency for Linux.

This is the first patch for our own D-Bus client library.
The D-Bus client code will be placed under 'dbus' on the top level directory
More patches will follow.


BUG=90036
TEST=try bot to make sure this won't break builds.

Review URL: http://codereview.chromium.org/7467031

git-svn-id: http://src.chromium.org/svn/trunk/src/build@93658 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

linux/system.gyp

@@ -395,6 +395,24 @@
       ],
     },
     {
+      'target_name': 'dbus',
+      'type': 'settings',
+      'direct_dependent_settings': {
+        'cflags': [
+          '<!@(<(pkg-config) --cflags dbus-1)',
+        ],
+      },
+      'link_settings': {
+        'ldflags': [
+          '<!@(<(pkg-config) --libs-only-L --libs-only-other dbus-1)',
+        ],
+        'libraries': [
+          '<!@(<(pkg-config) --libs-only-l dbus-1)',
+        ],
+      },
+    },
+    {
+      # TODO(satorux): Remove this once dbus-glib clients are gone.
       'target_name': 'dbus-glib',
       'type': 'settings',
       'direct_dependent_settings': {