Fix up certificate error reporting histograms

components/certificate_reporting/BUILD.gn

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//third_party/protobuf/proto_library.gni")
 
 # GYP version: components/certificate_reporting.gyp:certificate_reporting
 static_library("certificate_reporting") {
   sources = [
     "cert_logger.proto",
@@ skipping 33 matching lines @@
 source_set("unit_tests") {
   testonly = true
   sources = [
     "error_report_unittest.cc",
     "error_reporter_unittest.cc",
   ]
 
   deps = [
     ":certificate_reporting",
     "//base",
+    "//content/test:test_support",
     "//net:test_support",
     "//testing/gtest",
   ]
 }