Adds UMA to measure when the data reduction proxy via header is missing

components/data_reduction_proxy/browser/data_reduction_proxy_settings_test_utils.cc

Index: components/data_reduction_proxy/browser/data_reduction_proxy_settings_test_utils.cc
diff --git a/components/data_reduction_proxy/browser/data_reduction_proxy_settings_test_utils.cc b/components/data_reduction_proxy/browser/data_reduction_proxy_settings_test_utils.cc
index de7d98312022f2018263c4d96b1a3d081ba77720..e2b1d689743b795d92995756ee08fd01df9560b1 100644
--- a/components/data_reduction_proxy/browser/data_reduction_proxy_settings_test_utils.cc
+++ b/components/data_reduction_proxy/browser/data_reduction_proxy_settings_test_utils.cc
@@ -14,6 +14,7 @@
 #include "base/time/time.h"
 #include "components/data_reduction_proxy/browser/data_reduction_proxy_prefs.h"
 #include "components/data_reduction_proxy/browser/data_reduction_proxy_statistics_prefs.h"
+#include "components/data_reduction_proxy/common/data_reduction_proxy_headers_test_utils.h"
 #include "components/data_reduction_proxy/common/data_reduction_proxy_pref_names.h"
 #include "components/data_reduction_proxy/common/data_reduction_proxy_switches.h"
 
@@ -31,14 +32,6 @@ const char kProxy[] = "proxy";
 
 namespace data_reduction_proxy {
 
-// Transform "normal"-looking headers (\n-separated) to the appropriate
-// input format for ParseRawHeaders (\0-separated).
-void HeadersToRaw(std::string* headers) {
-  std::replace(headers->begin(), headers->end(), '\n', '\0');
-  if (!headers->empty())
-    *headers += '\0';
-}
-
 ProbeURLFetchResult FetchResult(bool enabled, bool success) {
   if (enabled) {
     if (success)