Fix Chrome OS build of update_engine.

Fix a typo in image_properties_chromeos.cc, $ifdef out an unused
constant in Chrome OS and adds the bspatch library to the Chrome OS
build.

Bug: None
Test: FEATURES=test emerge-link update_engine
Change-Id: I483da4b43b5cbd8b7349b0ff42973f97d197ba8e
diff --git a/libcurl_http_fetcher.cc b/libcurl_http_fetcher.cc
index f3d6a18..cb038a5 100644
--- a/libcurl_http_fetcher.cc
+++ b/libcurl_http_fetcher.cc
@@ -52,9 +52,6 @@
 
 const int kNoNetworkRetrySeconds = 10;
 
-// Socket tag used by all network sockets. See qtaguid kernel module for stats.
-const int kUpdateEngineSocketTag = 0x55417243;  // "CrAU" in little-endian.
-
 // libcurl's CURLOPT_SOCKOPTFUNCTION callback function. Called after the socket
 // is created but before it is connected. This callback tags the created socket
 // so the network usage can be tracked in Android.
@@ -62,6 +59,9 @@
                            curl_socket_t curlfd,
                            curlsocktype /* purpose */) {
 #ifdef __ANDROID__
+  // Socket tag used by all network sockets. See qtaguid kernel module for
+  // stats.
+  const int kUpdateEngineSocketTag = 0x55417243;  // "CrAU" in little-endian.
   qtaguid_tagSocket(curlfd, kUpdateEngineSocketTag, AID_OTA_UPDATE);
 #endif  // __ANDROID__
   return CURL_SOCKOPT_OK;