Implement native speech recognition for the launcher.

chrome/browser/ui/app_list/app_list_speech_recognizer.cc

+// 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.
+
+#include "chrome/browser/ui/app_list/app_list_speech_recognizer.h"
+
+#include <algorithm>
+
+#include "base/bind.h"
+#include "base/strings/string16.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/ui/app_list/start_page_service.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/render_process_host.h"
+#include "content/public/browser/speech_recognition_manager.h"
+#include "content/public/browser/speech_recognition_session_config.h"
+#include "content/public/common/speech_recognition_error.h"
+#include "ui/app_list/speech_ui_model_observer.h"

[Lei Zhang, 2014/10/30 05:15:42]

not used?

[Anand Mistry (off Chromium), 2014/10/31 00:50:06]

For SpeechRecognitionState, but also declared in the header.

+
+namespace app_list {
+
+// 5 second timeout to cancel if there's no speech heard.
+static const int kNoSpeechTimeout = 5;

[Lei Zhang, 2014/10/30 05:15:42]

Add "InSeconds" to the name so it's obvious you got the units correct.

[Anand Mistry (off Chromium), 2014/10/31 00:50:06]

Done.

+
+AppListSpeechRecognizer::AppListSpeechRecognizer(
+    StartPageService* start_page_service,
+    const std::string& locale)
+    : start_page_service_(start_page_service),
+      locale_(locale),
+      speech_timeout_(false, false),
+      session_(-1),
+      weak_factory_(this) {
+}
+
+AppListSpeechRecognizer::~AppListSpeechRecognizer() {
+}
+
+void AppListSpeechRecognizer::Start() {
+  // The speech recognizer checks to see if the request is allowed by looking
+  // up the renderer process. A renderer containing the app-list is hard-coded
+  // to be allowed.
+  // TODO(amistry): Somehow eliminate this dependency.
+  content::WebContents* contents =
+      start_page_service_->GetSpeechRecognitionContents();
+  if (!contents)
+    return;
+
+  content::BrowserThread::PostTask(
+      content::BrowserThread::IO,
+      FROM_HERE,
+      base::Bind(&AppListSpeechRecognizer::StartOnIOThread,
+                 this,
+                 contents->GetRenderProcessHost()->GetID(),
+                 make_scoped_refptr(
+                     start_page_service_->profile()->GetRequestContext())));
+}
+
+void AppListSpeechRecognizer::StartOnIOThread(
+    int render_process_id,
+    scoped_refptr<net::URLRequestContextGetter> url_request_context_getter) {

[Lei Zhang, 2014/10/30 05:15:42]

You should add a DCHECK_CURRENTLY_ON() call here, same with StopOnIOThread().

Please use it liberally with other methods. It's not clear what methods should
run on what thread, and what variables should be accessed on which thread. If
you can avoid having a multi-threaded class, even better.

[Anand Mistry (off Chromium), 2014/10/31 00:50:06]

Done.
Unfortunately, it can't be avoided. The speech recognizer must be used from the
IO thread, but this class needs to be used from the UI thread.

[Lei Zhang, 2014/10/31 01:18:04]

An alternate strategy that may work is to have SpeechRecognizer live completely
on the UI thread, and internal to speech_recognizer.cc, have a class that lives
on the IO thread, with the two classes using PostTask() to talk to each other.
Then each of the two classes is thread-safe and it's easier to reason about
their correctness.

[Anand Mistry (off Chromium), 2014/11/03 06:51:55]

I've tried to do this, and the lifecycle is more correct now. But it's kinda
complicated.

+  if (session_ != -1)
+    StopOnIOThread();
+
+  content::SpeechRecognitionSessionConfig config;
+  config.language = locale_;
+  config.is_legacy_api = false;
+  config.continuous = true;
+  config.interim_results = true;
+  config.max_hypotheses = 1;
+  config.filter_profanities = true;
+  config.url_request_context_getter = url_request_context_getter;
+  config.event_listener = weak_factory_.GetWeakPtr();
+  config.initial_context.render_process_id = render_process_id;
+
+  auto speech_instance = content::SpeechRecognitionManager::GetInstance();
+  session_ = speech_instance->CreateSession(config);
+  speech_instance->StartSession(session_);
+}
+
+void AppListSpeechRecognizer::Stop() {
+  content::BrowserThread::PostTask(
+      content::BrowserThread::IO,
+      FROM_HERE,
+      base::Bind(&AppListSpeechRecognizer::StopOnIOThread, this));
+}
+
+void AppListSpeechRecognizer::StopOnIOThread() {
+  if (session_ == -1)
+    return;
+
+  // Prevent recursion.
+  int session = session_;
+  session_ = -1;
+  StopSpeechTimeout();
+  content::SpeechRecognitionManager::GetInstance()->StopAudioCaptureForSession(
+      session);
+}
+
+void AppListSpeechRecognizer::NotifyRecognitionStateChanged(
+    SpeechRecognitionState new_state) {
+  content::BrowserThread::PostTask(
+      content::BrowserThread::UI,
+      FROM_HERE,
+      base::Bind(&StartPageService::OnSpeechRecognitionStateChanged,
+                 base::Unretained(start_page_service_),
+                 new_state));
+}
+
+void AppListSpeechRecognizer::StartSpeechTimeout() {
+  content::BrowserThread::PostTask(
+      content::BrowserThread::UI,
+      FROM_HERE,
+      base::Bind(&base::Timer::Start,
+                 base::Unretained(&speech_timeout_),
+                 FROM_HERE,
+                 base::TimeDelta::FromSeconds(kNoSpeechTimeout),
+                 base::Bind(&AppListSpeechRecognizer::SpeechTimeout, this)));
+}
+
+void AppListSpeechRecognizer::StopSpeechTimeout() {
+  content::BrowserThread::PostTask(
+      content::BrowserThread::UI,
+      FROM_HERE,
+      base::Bind(&base::Timer::Stop,
+                 base::Unretained(&speech_timeout_)));
+}
+
+void AppListSpeechRecognizer::SpeechTimeout() {
+  Stop();
+}
+
+void AppListSpeechRecognizer::OnRecognitionStart(int session_id) {
+  NotifyRecognitionStateChanged(SPEECH_RECOGNITION_RECOGNIZING);
+}
+
+void AppListSpeechRecognizer::OnRecognitionEnd(int session_id) {
+  StopOnIOThread();
+  NotifyRecognitionStateChanged(SPEECH_RECOGNITION_READY);
+}
+
+void AppListSpeechRecognizer::OnRecognitionResults(
+    int session_id, const content::SpeechRecognitionResults& results) {
+  base::string16 result_str;
+  unsigned int final_count = 0;

[Lei Zhang, 2014/10/30 05:15:42]

use size_t

[Anand Mistry (off Chromium), 2014/10/31 00:50:06]

Done.

+  for (const auto& result : results) {
+    if (!result.is_provisional)
+      final_count++;
+    result_str += result.hypotheses[0].utterance;
+  }
+  StopSpeechTimeout();
+  content::BrowserThread::PostTask(
+      content::BrowserThread::UI,
+      FROM_HERE,
+      base::Bind(&StartPageService::OnSpeechResult,
+                 base::Unretained(start_page_service_),
+                 result_str,
+                 final_count == results.size()));
+
+  // Stop the moment we have a final result.
+  if (final_count == results.size())
+    StopOnIOThread();
+}
+
+void AppListSpeechRecognizer::OnRecognitionError(
+    int session_id, const content::SpeechRecognitionError& error) {
+  StopOnIOThread();
+  if (error.code == content::SPEECH_RECOGNITION_ERROR_NETWORK) {
+    NotifyRecognitionStateChanged(SPEECH_RECOGNITION_NETWORK_ERROR);
+  }
+  NotifyRecognitionStateChanged(SPEECH_RECOGNITION_READY);
+}
+
+void AppListSpeechRecognizer::OnSoundStart(int session_id) {
+  StartSpeechTimeout();
+  NotifyRecognitionStateChanged(SPEECH_RECOGNITION_IN_SPEECH);
+}
+
+void AppListSpeechRecognizer::OnSoundEnd(int session_id) {
+  StopOnIOThread();
+  NotifyRecognitionStateChanged(SPEECH_RECOGNITION_RECOGNIZING);
+}
+
+void AppListSpeechRecognizer::OnAudioLevelsChange(
+    int session_id, float volume, float noise_volume) {
+  volume = std::max(0.0f, volume - noise_volume);
+  int16_t sound_level = static_cast<int16_t>(INT16_MAX * volume);

[Lei Zhang, 2014/10/30 05:15:42]

can't this overflow if |volume| > 1 ?

[Anand Mistry (off Chromium), 2014/10/31 00:50:06]

It is defined to be in the range [0.0, 1.0]

[Lei Zhang, 2014/10/31 01:18:04]

Add a DCHECK?

[Anand Mistry (off Chromium), 2014/11/03 06:51:55]

Done.

+  content::BrowserThread::PostTask(
+      content::BrowserThread::UI,
+      FROM_HERE,
+      base::Bind(&StartPageService::OnSpeechSoundLevelChanged,
+                 base::Unretained(start_page_service_),
+                 sound_level));
+}
+
+}  // namespace app_list