Remove unused HostResolver::Observer.

net/base/test_host_resolver_observer.cc

-// Copyright (c) 2011 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.
-
-#include "net/base/test_host_resolver_observer.h"
-
-namespace net {
-
-bool operator==(const HostResolver::RequestInfo& a,
-                const HostResolver::RequestInfo& b) {
-   return a.hostname() == b.hostname() &&
-          a.port() == b.port() &&
-          a.allow_cached_response() == b.allow_cached_response() &&
-          a.priority() == b.priority() &&
-          a.is_speculative() == b.is_speculative() &&
-          a.referrer() == b.referrer();
-}
-
-TestHostResolverObserver::TestHostResolverObserver() {
-}
-
-TestHostResolverObserver::~TestHostResolverObserver() {
-}
-
-void TestHostResolverObserver::OnStartResolution(
-    int id,
-    const HostResolver::RequestInfo& info) {
-  start_log.push_back(StartOrCancelEntry(id, info));
-}
-
-void TestHostResolverObserver::OnFinishResolutionWithStatus(
-    int id,
-    bool was_resolved,
-    const HostResolver::RequestInfo& info) {
-  finish_log.push_back(FinishEntry(id, was_resolved, info));
-}
-
-void TestHostResolverObserver::OnCancelResolution(
-    int id,
-    const HostResolver::RequestInfo& info) {
-  cancel_log.push_back(StartOrCancelEntry(id, info));
-}
-
-}  // namespace