Implement HttpUserAgentSettings delegate for Android WebView

android_webview/browser/net/aw_http_user_agent_settings.h

+// Copyright (c) 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.
+
+#ifndef ANDROID_WEBVIEW_BROWSER_NET_AW_HTTP_USER_AGENT_SETTINGS_H_
+#define ANDROID_WEBVIEW_BROWSER_NET_AW_HTTP_USER_AGENT_SETTINGS_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "net/url_request/http_user_agent_settings.h"
+
+namespace android_webview {
+
+// An implementation of |HttpUserAgentSettings| that provides HTTP header
+// Accept-Language value that tracks aw accept language.
+class AwHttpUserAgentSettings : public net::HttpUserAgentSettings {
+ public:
+  // Must be called on the UI thread.
+  explicit AwHttpUserAgentSettings();

[Torne, 2015/07/17 13:33:19]

explicit is only for 1-arg constructors.

[ctserng, 2015/07/17 16:51:15]

Will do.

+  // Must be called on the IO thread.

[Torne, 2015/07/17 13:33:19]

Explicitly requiring this to be destructed on a different thread than it's
created on seems really weird. It's generally preferred for objects to be used
only on a single thread where possible.

[ctserng, 2015/07/17 16:51:15]

I understand this, but the life cycle of AwURLRequestContextGetter seems to
imply that the object is created on the UI thread but then exists on the IO
thread.

This code is templated from chrome_http_user_agent_settings.h

https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/net...

+  ~AwHttpUserAgentSettings() override;
+
+  // net::HttpUserAgentSettings implementation
+  std::string GetAcceptLanguage() const override;
+  std::string GetUserAgent() const override;
+
+ private:
+  // Avoid re-processing by caching the last value from the locale and the
+  // last result of processing via net::HttpUtil::GenerateAccept*Header().
+  mutable std::string last_aw_accept_language_;
+  mutable std::string last_http_accept_language_;
+
+  DISALLOW_COPY_AND_ASSIGN(AwHttpUserAgentSettings);
+};
+
+}  // namespace android_webview
+
+#endif  // ANDROID_WEBVIEW_BROWSER_NET_AW_HTTP_USER_AGENT_SETTINGS_H_
+