update_engine: Breaks the use of libcros into two dbus proxies.

This CL breaks USE_LIBCROS into two defines:
	USE_CHROME_NETWORK_PROXY
	USE_CHROME_KIOSK_APP
and changes all related build artifacts for both chrome and android.

Breaks USE_libcros into USE_chrome_network_proxy and USE_chrome_kiosk_app.
Removes BRILL_USE_LIBCROS.
Replaces __BRILLO__ with USE_OMAHA.

BUG=chromium:717306
TEST=Ran test 'cros_workon_make --board=amd64-generic --test update_engine'
	for all four conditions of the newly introduced two flags.

Change-Id: I9ca5b35c22a17c45a861db6a434239096a896127
Reviewed-on: https://chromium-review.googlesource.com/596802
Commit-Ready: Amin Hassani <ahassani@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Tested-by: Sen Jiang <senj@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Sen Jiang <senj@chromium.org>
diff --git a/update_manager/real_system_provider.h b/update_manager/real_system_provider.h
index a62e1ae..80a8615 100644
--- a/update_manager/real_system_provider.h
+++ b/update_manager/real_system_provider.h
@@ -40,8 +40,12 @@
       chromeos_update_engine::BootControlInterface* boot_control,
       org::chromium::LibCrosServiceInterfaceProxyInterface* libcros_proxy)
       : hardware_(hardware),
+#if USE_CHROME_KIOSK_APP
         boot_control_(boot_control),
         libcros_proxy_(libcros_proxy) {}
+#else
+        boot_control_(boot_control) {}
+#endif  // USE_CHROME_KIOSK_APP
 
   // Initializes the provider and returns whether it succeeded.
   bool Init();
@@ -78,8 +82,9 @@
 
   chromeos_update_engine::HardwareInterface* const hardware_;
   chromeos_update_engine::BootControlInterface* const boot_control_;
-  org::chromium::LibCrosServiceInterfaceProxyInterface* const libcros_proxy_
-      ALLOW_UNUSED_TYPE;
+#if USE_CHROME_KIOSK_APP
+  org::chromium::LibCrosServiceInterfaceProxyInterface* const libcros_proxy_;
+#endif  // USE_CHROME_KIOSK_APP
 
   DISALLOW_COPY_AND_ASSIGN(RealSystemProvider);
 };