Add Certificate Transparency logs auditing

components/certificate_transparency/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.
 
 source_set("certificate_transparency") {
   sources = [
     "log_proof_fetcher.cc",
     "log_proof_fetcher.h",
+    "observed_leaf.cc",
+    "observed_leaf.h",
     "single_tree_tracker.cc",
     "single_tree_tracker.h",
     "tree_state_tracker.cc",
     "tree_state_tracker.h",
   ]
 
   deps = [
     "//base",
     "//components/safe_json",
     "//net",
     "//url",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "log_proof_fetcher_unittest.cc",
     "single_tree_tracker_unittest.cc",
   ]
 
   deps = [
     ":certificate_transparency",
     "//base/test:test_support",
     "//components/safe_json:test_support",
     "//net:test_support",
     "//testing/gtest",
   ]
 }