Implement offline mode behind a flag

content/browser/loader/offline_policy.cc

+// Copyright (c) 2013 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 "content/browser/loader/offline_policy.h"
+
+#include "base/command_line.h"
+#include "content/public/common/content_switches.h"
+#include "net/base/load_flags.h"
+#include "net/http/http_response_info.h"
+#include "net/url_request/url_request.h"
+
+namespace content {
+
+OfflinePolicy::OfflinePolicy()
+    : offline_state_(INIT) {}
+
+OfflinePolicy::~OfflinePolicy() {}
+
+int OfflinePolicy::GetAdditionalLoadFlags(
+    int current_flags, ResourceType::Type resource_type) {
+
+  // Don't do anything if offline mode is disabled.
+  if (!CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableOfflineCacheAccess))
+    return 0;
+
+  if (resource_type == ResourceType::MAIN_FRAME)
+    offline_state_ = INIT;
+
+  // If a consumer has requested something contradictory, it wins; we
+  // don't modify the load flags.
+  if (current_flags &
+      (net::LOAD_BYPASS_CACHE | net::LOAD_PREFERRING_CACHE |
+       net::LOAD_ONLY_FROM_CACHE | net::LOAD_FROM_CACHE_IF_OFFLINE |
+       net::LOAD_DISABLE_CACHE)) {
+    return 0;
+  }
+
+  switch(offline_state_) {
+    case INIT:
+      return net::LOAD_FROM_CACHE_IF_OFFLINE;
+    case ONLINE:
+      return 0;
+    case OFFLINE:
+      return net::LOAD_ONLY_FROM_CACHE;
+  }
+  NOTREACHED();
+  return 0;
+}
+
+void OfflinePolicy::RequestCompleted(
+    const net::HttpResponseInfo& response_info) {
+  // Don't do anything if offline mode is disabled.
+  if (!CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableOfflineCacheAccess))
+    return;
+
+  if (offline_state_ != INIT)
+    // We've already made the decision for the rest of this set
+    // of navigations.
+    return;
+
+  if (response_info.server_data_unavailable) {
+    offline_state_ = OFFLINE;
+  } else if (response_info.network_accessed) {
+    // If we got the response from the network or validated it as part
+    // of this request, that means our connection to the host is working.
+    offline_state_ = ONLINE;
+  }
+}
+
+}  // namespace content