libweave: Copy data_encoding.cc into libweave

It's reducing dependency on libchromeos.

BUG=brillo:1257
TEST=`FEATURES=test emerge-gizmo libweave buffet`

Change-Id: I8356302accb368e717777fd578caa2ba018a29dd
Reviewed-on: https://chromium-review.googlesource.com/293631
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
Trybot-Ready: Vitaly Buka <vitalybuka@chromium.org>
Tested-by: Vitaly Buka <vitalybuka@chromium.org>
diff --git a/libweave/src/notification/xmpp_channel.cc b/libweave/src/notification/xmpp_channel.cc
index 13a3565..2715dd9 100644
--- a/libweave/src/notification/xmpp_channel.cc
+++ b/libweave/src/notification/xmpp_channel.cc
@@ -7,11 +7,11 @@
 #include <string>
 
 #include <base/bind.h>
-#include <chromeos/data_encoding.h>
 #include <weave/network.h>
 #include <weave/task_runner.h>
 
 #include "libweave/src/backoff_entry.h"
+#include "libweave/src/data_encoding.h"
 #include "libweave/src/notification/notification_delegate.h"
 #include "libweave/src/notification/notification_parser.h"
 #include "libweave/src/notification/xml_node.h"
@@ -40,7 +40,7 @@
       "auth:allow-non-google-login='true' "
       "auth:client-uses-full-bind-result='true' "
       "xmlns:auth='http://www.google.com/talk/protocol/auth'>" +
-      chromeos::data_encoding::Base64Encode(credentials) + "</auth>";
+      Base64Encode(credentials) + "</auth>";
   return msg;
 }
 
@@ -278,7 +278,7 @@
   }
   std::string data = node->text();
   std::string json_data;
-  if (!chromeos::data_encoding::Base64Decode(data, &json_data)) {
+  if (!Base64Decode(data, &json_data)) {
     LOG(WARNING) << "Failed to decode base64-encoded message payload: " << data;
     return;
   }