metrics: protobufs need to be uploaded as binary

TEST=manually tested on panther_embedded
BUG=none

Change-Id: Id07952d2b015c4199344556686218a78b8d79193
Reviewed-on: https://chromium-review.googlesource.com/221060
Reviewed-by: Bertrand Simonnet <bsimonnet@chromium.org>
Commit-Queue: Nathan Bullock <nathanbullock@google.com>
Tested-by: Nathan Bullock <nathanbullock@google.com>
diff --git a/metrics/uploader/sender_http.cc b/metrics/uploader/sender_http.cc
index 7b5228a..ff417b3 100644
--- a/metrics/uploader/sender_http.cc
+++ b/metrics/uploader/sender_http.cc
@@ -21,9 +21,10 @@
 
   chromeos::http::HeaderList headers = {{"X-Chrome-UMA-Log-SHA1", hash}};
   chromeos::ErrorPtr error;
-  auto response = chromeos::http::PostText(
+  auto response = chromeos::http::PostBinary(
       server_url_,
       content.c_str(),
+      content.size(),
       chromeos::mime::application::kWwwFormUrlEncoded,
       headers,
       chromeos::http::Transport::CreateDefault(),