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/SConstruct b/SConstruct
index f75b256..dea012d 100644
--- a/SConstruct
+++ b/SConstruct
@@ -238,6 +238,7 @@
                    buffered_file_writer.cc
                    bzip.cc
                    bzip_extent_writer.cc
+                   chrome_browser_proxy_resolver.cc
                    chrome_proxy_resolver.cc
                    cycle_breaker.cc
                    dbus_service.cc
@@ -285,6 +286,7 @@
                             action_processor_unittest.cc
                             buffered_file_writer_unittest.cc
                             bzip_extent_writer_unittest.cc
+                            chrome_browser_proxy_resolver_unittest.cc
                             chrome_proxy_resolver_unittest.cc
                             cycle_breaker_unittest.cc
                             decompressing_file_writer_unittest.cc