Add a header when fetching pages under the DMServer URL.

components/policy/core/browser/policy_header_io_helper.cc

Index: components/policy/core/browser/policy_header_io_helper.cc
diff --git a/components/policy/core/browser/policy_header_io_helper.cc b/components/policy/core/browser/policy_header_io_helper.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e1680189f71cc1e7951051ef3b907c19ac944bfc
--- /dev/null
+++ b/components/policy/core/browser/policy_header_io_helper.cc
@@ -0,0 +1,60 @@
+// 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 "components/policy/core/browser/policy_header_io_helper.h"
+
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/sequenced_task_runner.h"
+#include "net/url_request/url_request.h"
+
+namespace {
+
+// The name of the header containing the policy information.
+const char kChromePolicyHeader[] = "Chrome-Policy-Posture";
+
+}  // namespace
+
+namespace policy {
+
+PolicyHeaderIOHelper::PolicyHeaderIOHelper(
+    const std::string& server_url,
+    const std::string& initial_header_value,
+    scoped_refptr<base::SequencedTaskRunner> task_runner)
+    : server_url_(server_url),
+      task_runner_(task_runner),
+      policy_header_(initial_header_value),
+      weak_factory_(this) {
+}
+
+PolicyHeaderIOHelper::~PolicyHeaderIOHelper() {
+}
+
+// Sets any necessary policy headers on the passed request.
+void PolicyHeaderIOHelper::AddPolicyHeaders(net::URLRequest* request) const {
+  DCHECK(task_runner_->RunsTasksOnCurrentThread());
+  const GURL& url = request->url();
+  if (!policy_header_.empty() &&
+      url.spec().compare(0, server_url_.size(), server_url_) == 0) {
+    request->SetExtraRequestHeaderByName(kChromePolicyHeader,
+                                         policy_header_,
+                                         true /* overwrite */);
+  }
+}
+
+void PolicyHeaderIOHelper::UpdateHeader(const std::string& new_header) {
+  // Post a task to the IO thread to modify this.
+  task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&PolicyHeaderIOHelper::UpdateHeaderOnTaskRunner,
+                 weak_factory_.GetWeakPtr(), new_header));

[willchan no longer on Chromium, 2013/12/10 23:27:09]

Is this correct? It looks like the WeakPtr is acquired on the UI thread and
destroyed on the IO thread. GetWeakPtr() will set the thread for the WeakPtr,
and it's not threadsafe...

Furthermore, stuff owned by ProfileIOData will always get deleted on the IO
thread after the Profile is already destroyed on the UI thread. So UI=>IO thread
is always safe, whereas IO=>UI task posting must be protected by a WeakPtr.

In short, I think you should just ditch the WeakPtr stuff here.

[Andrew T Wilson (Slow), 2013/12/10 23:53:06]

Done. Makes sense to me.

+}
+
+void PolicyHeaderIOHelper::UpdateHeaderOnTaskRunner(
+    const std::string& new_header) {
+  DCHECK(task_runner_->RunsTasksOnCurrentThread());
+  policy_header_ = new_header;
+}
+
+}  // namespace policy