Automatically trigger installation of high-quality speech synthesis extension.

chrome/browser/chromeos/extensions/speech_synthesis_loader.h

+// 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.
+
+#ifndef CHROME_BROWSER_CHROMEOS_EXTENSIONS_SPEECH_SYNTHESIS_LOADER_H_
+#define CHROME_BROWSER_CHROMEOS_EXTENSIONS_SPEECH_SYNTHESIS_LOADER_H_
+
+#include "base/containers/hash_tables.h"
+#include "base/memory/weak_ptr.h"
+#include "base/prefs/pref_change_registrar.h"
+#include "chrome/browser/extensions/external_loader.h"
+#include "chrome/browser/profiles/profile.h"
+
+namespace user_prefs {
+class PrefRegistrySyncable;
+}
+
+class PrefChanceRegistrar;
+
+namespace chromeos {
+
+// Chrome OS comes with medium-quality speech synthesis extensions built-in.
+// When the user speaks a certain threshold of utterances in the same session,
+// we set a preference indicating that high quality speech is enabled for that
+// language. This class is the external extension loader that checks the
+// preference and prepares the list of external extensions to be installed
+// from the web store automatically. The high-quality speech synthesis
+// extensions are installed silently as component extensions.
+class SpeechSynthesisLoader
+    : public extensions::ExternalLoader,
+      public base::SupportsWeakPtr<SpeechSynthesisLoader> {
+ public:
+  explicit SpeechSynthesisLoader(Profile* profile);
+  virtual ~SpeechSynthesisLoader();
+
+  // Implementation of extensions::ExternalLoader:
+  virtual void StartLoading() OVERRIDE;
+
+  // Register speech synthesis prefs for a profile.
+  static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
+
+ private:
+  // The profile that this loader is associated with. It listens for
+  // preference changes for that profile.
+  Profile* profile_;
+
+  // The pref change registrar, so we can watch for pref changes.
+  scoped_ptr<PrefChangeRegistrar> pref_change_registrar_;
+
+  // A weak ptr factory, so we can safely bind pref change registrar
+  // callbacks to this class.
+  base::WeakPtrFactory<SpeechSynthesisLoader> weak_ptr_factory_;
+
+  // A map from language code to the extension id of the high-quality
+  // extension for that language in the web store, if any.
+  base::hash_map<std::string, std::string> lang_to_extension_id_map_;
+
+  DISALLOW_COPY_AND_ASSIGN(SpeechSynthesisLoader);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_EXTENSIONS_SPEECH_SYNTHESIS_LOADER_H_