Implement native speech recognition for the launcher.

chrome/browser/ui/app_list/speech_recognizer.h

+// Copyright 2014 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_UI_APP_LIST_SPEECH_RECOGNIZER_H_
+#define CHROME_BROWSER_UI_APP_LIST_SPEECH_RECOGNIZER_H_
+
+#include <string>
+
+#include "base/memory/weak_ptr.h"
+
+namespace net {
+class URLRequestContextGetter;
+}
+
+namespace app_list {
+
+class SpeechRecognizerDelegate;
+
+// SpeechRecognizer is a wrapper around the speech recognition engine that
+// simplifies its use from the UI thread. This class handles all setup/shutdown,
+// collection of results, error cases, and threading.
+class SpeechRecognizer {
+ public:
+  SpeechRecognizer(SpeechRecognizerDelegate* delegate,
+                   net::URLRequestContextGetter* url_request_context_getter,
+                   const std::string& locale);
+  ~SpeechRecognizer();
+
+  // Start/stop the speech recognizer. Must be called on the UI thread.
+  void Start();
+  void Stop();
+
+ private:
+  class EventListener;
+
+  SpeechRecognizerDelegate* delegate_;  // Not owned.

[Lei Zhang, 2014/11/05 03:44:38]

Can you just use save the content::WebContents* instead?

[Anand Mistry (off Chromium), 2014/11/05 04:44:11]

No, because it might change. However, the current one will always be available
via SpeechRecognizerDelegate.

+  scoped_refptr<EventListener> speech_event_listener_;
+
+  // Weak pointer to pass to EventListener.
+  base::WeakPtrFactory<SpeechRecognizerDelegate> delegate_weak_factory_;

[Lei Zhang, 2014/11/05 03:44:38]

The delegate should have its own WeakPtrFactory() and hand out WeakPtrs. i.e.
SpeechRecognizer should take in const WeakPtr<SpeechRecognizerDelegate>&

[Anand Mistry (off Chromium), 2014/11/05 04:44:11]

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(SpeechRecognizer);
+};
+
+}  // namespace app_list
+
+#endif  // CHROME_BROWSER_UI_APP_LIST_SPEECH_RECOGNIZER_H_