AU: Full proxy support

This CL Introduces a new proxy resolver that queries Chrome browser
for all URLs. This means the updater now works with Proxy
AutoConfiguration (PAC) files and automatic proxy detection.

BUG=chromium-os:9478
TEST=performed update, unittests

Review URL: http://codereview.chromium.org/6594025

Change-Id: I2c169aec06109e3eabc4011e0b536685dfd13f79
diff --git a/UpdateEngine.conf b/UpdateEngine.conf
index 534fade..949e5bb 100644
--- a/UpdateEngine.conf
+++ b/UpdateEngine.conf
@@ -28,6 +28,7 @@
     <allow send_destination="org.chromium.UpdateEngine"
            send_interface="org.chromium.UpdateEngineInterface"
            send_member="SetTrack"/>
+    <allow send_interface="org.chromium.UpdateEngineLibcrosProxyResolvedInterface" />
   </policy>
   <policy context="default">
     <deny send_destination="org.chromium.UpdateEngine" />