[Hotword] Delay checking for audio devices until needed.

chrome/browser/search/hotword_service.cc

 // Copyright 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 "chrome/browser/search/hotword_service.h"
 
 #include "base/command_line.h"
 #include "base/i18n/case_conversion.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
@@ skipping 197 matching lines @@
   }
   UMA_HISTOGRAM_ENUMERATION("Hotword.Enabled", enabled_state,
                             NUM_HOTWORD_ENABLED_METRICS);
 
   pref_registrar_.Init(profile_->GetPrefs());
   pref_registrar_.Add(
       prefs::kHotwordSearchEnabled,
       base::Bind(&HotwordService::OnHotwordSearchEnabledChanged,
                  base::Unretained(this)));
 
-  registrar_.Add(this,
-                 chrome::NOTIFICATION_BROWSER_WINDOW_READY,
-                 content::NotificationService::AllSources());
-
   extensions::ExtensionSystem::Get(profile_)->ready().Post(
       FROM_HERE,
       base::Bind(base::IgnoreResult(
           &HotwordService::MaybeReinstallHotwordExtension),
                  weak_factory_.GetWeakPtr()));
 
   // Clear the old user pref because it became unusable.
   // TODO(rlp): Remove this code per crbug.com/358789.
   if (profile_->GetPrefs()->HasPrefPath(
           hotword_internal::kHotwordUnusablePrefName)) {
     profile_->GetPrefs()->ClearPref(hotword_internal::kHotwordUnusablePrefName);
   }
 }
 
 HotwordService::~HotwordService() {
 }
 
-void HotwordService::Observe(int type,
-                             const content::NotificationSource& source,
-                             const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_BROWSER_WINDOW_READY) {
-    // The microphone monitor must be initialized as the page is loading
-    // so that the state of the microphone is available when the page
-    // loads. The Ok Google Hotword setting will display an error if there
-    // is no microphone but this information will not be up-to-date unless
-    // the monitor had already been started. Furthermore, the pop up to
-    // opt in to hotwording won't be available if it thinks there is no
-    // microphone. There is no hard guarantee that the monitor will actually
-    // be up by the time it's needed, but this is the best we can do without
-    // starting it at start up which slows down start up too much.
-    // The content/media for microphone uses the same observer design and
-    // makes use of the same audio device monitor.
-    HotwordServiceFactory::GetInstance()->UpdateMicrophoneState();
-  }
-}
-
 void HotwordService::OnExtensionUninstalled(
     content::BrowserContext* browser_context,
     const extensions::Extension* extension,
     extensions::UninstallReason reason) {
   CHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 
   if (extension->id() != extension_misc::kHotwordExtensionId ||
       profile_ != Profile::FromBrowserContext(browser_context) ||
       !GetExtensionService(profile_))
     return;
@@ skipping 140 matching lines @@
     PluginPrefs* plugin_prefs = PluginPrefs::GetForProfile(profile_).get();
     if (content::PluginService::GetInstance()->GetPluginInfoByPath(path, &info))
       nacl_enabled = plugin_prefs->IsPluginEnabled(info);
   }
   if (!nacl_enabled)
     error_message_ = IDS_HOTWORD_NACL_DISABLED_ERROR_MESSAGE;
 
   RecordErrorMetrics(error_message_);
 
   // Determine if the proper audio capabilities exist.
-  bool audio_capture_allowed =
-      profile_->GetPrefs()->GetBoolean(prefs::kAudioCaptureAllowed);
-  if (!audio_capture_allowed || !HotwordServiceFactory::IsMicrophoneAvailable())
-    error_message_ = IDS_HOTWORD_MICROPHONE_ERROR_MESSAGE;
+  // The first time this is called, it probably won't return in time, but that's
+  // why it won't be included in the error calculation (i.e., the call to
+  // IsAudioDeviceStateUpdated()). However, this use case is rare and typically
+  // the devices will be initialized by the time a user goes to settings.
+  bool audio_device_state_updated =
+      HotwordServiceFactory::IsAudioDeviceStateUpdated();
+  HotwordServiceFactory::GetInstance()->UpdateMicrophoneState();

[Anand Mistry (off Chromium), 2014/10/17 20:32:42]

If you call UpdateMicrophoneState() first, then IsAudioDeviceStateUpdated() will
always return true since the  former call will always update the audio state
(since it calls HotwordServiceFactory::OnUpdateAudioDevices()). Timing wise, the
ordering of these two statements won't matter. But moving
UpdateMicrophoneState() first will eliminate all the device state logic.

[rpetterson, 2014/10/20 06:25:50]

Thanks for your comment. It made me look a little deeper and I realized the
OnUpdateAudioDevices is actually called after devices have been enumerated. I've
removed the call to OnUpdateAudioDevices in UpdateMicrophoneState in
hotword_service_factory.cc and I think this logic here now makes more sense.
PTAL.

+  if (audio_device_state_updated) {
+    bool audio_capture_allowed =
+        profile_->GetPrefs()->GetBoolean(prefs::kAudioCaptureAllowed);
+    if (!audio_capture_allowed ||
+        !HotwordServiceFactory::IsMicrophoneAvailable())
+      error_message_ = IDS_HOTWORD_MICROPHONE_ERROR_MESSAGE;
+  }
 
   return (error_message_ == 0) && IsHotwordAllowed();
 }
 
 bool HotwordService::IsHotwordAllowed() {
   std::string group = base::FieldTrialList::FindFullName(
       hotword_internal::kHotwordFieldTrialName);
   return !group.empty() &&
       group != hotword_internal::kHotwordFieldTrialDisabledGroupName &&
       DoesHotwordSupportLanguage(profile_);
@@ skipping 99 matching lines @@
     return false;
 
   std::string previous_locale =
       profile_->GetPrefs()->GetString(prefs::kHotwordPreviousLanguage);
   std::string locale = GetCurrentLocale(profile_);
 
   // If it's a new locale, then the old extension should be uninstalled.
   return locale != previous_locale &&
       HotwordService::DoesHotwordSupportLanguage(profile_);
 }