[Hotword] Set up hotwording to be externally loaded component extension. Only load if the field tri…

chrome/browser/extensions/external_component_loader.cc

 // 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.
 
 #include "chrome/browser/extensions/external_component_loader.h"
 
 #include "base/command_line.h"
+#include "base/i18n/case_conversion.h"
+#include "base/metrics/field_trial.h"
 #include "base/prefs/pref_change_registrar.h"
 #include "base/prefs/pref_service.h"
 #include "base/values.h"
 #include "chrome/browser/bookmarks/enhanced_bookmarks_features.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/external_provider_impl.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/extensions/extension_constants.h"
 #include "chrome/common/pref_names.h"
 #include "components/user_prefs/pref_registry_syncable.h"
 #include "content/public/browser/browser_thread.h"
+#include "ui/base/l10n/l10n_util.h"
 
 namespace extensions {
 
 #if defined(OS_CHROMEOS)
 namespace {
 // Table mapping language codes to the extension ids of high-quality
 // speech synthesis extensions. See the comment in StartLoading() for more.
 struct LangToExtensionId {
   const char* lang;
   const char* extension_id;
@@ skipping 22 matching lines @@
 
 ExternalComponentLoader::~ExternalComponentLoader() {}
 
 void ExternalComponentLoader::StartLoading() {
   CHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
   prefs_.reset(new base::DictionaryValue());
   std::string appId = extension_misc::kInAppPaymentsSupportAppId;
   prefs_->SetString(appId + ".external_update_url",
                     extension_urls::GetWebstoreUpdateUrl().spec());
 
+  std::string group = base::FieldTrialList::FindFullName("VoiceTrigger");
+  std::string locale =
+#if defined(OS_CHROMEOS)
+      // On ChromeOS locale is per-profile.
+      profile_->GetPrefs()->GetString(prefs::kApplicationLocale);
+#else
+      g_browser_process->GetApplicationLocale();
+#endif

[asargent_no_longer_on_chrome, 2014/01/30 00:22:56]

optional: would it make sense to have a common method (somewhere in
chrome/browser/ perhaps) that abstracts getting the locale, so each call site
doesn't have to have their code littered with #ifdef's? 

[rpetterson, 2014/01/30 00:46:09]

Yes, I actually have plans to do this in another CL since we'll need it
elsewhere. So this will get cleaned up then.

+  // Only available for English now.
+  std::string normalized_locale = l10n_util::NormalizeLocale(locale);
+  bool locale_available =
+      !(strcmp(normalized_locale.c_str(), "en")) ||
+      !(strcmp(normalized_locale.c_str(), "en_us")) ||
+      !(strcmp(normalized_locale.c_str(), "en_US"));

[asargent_no_longer_on_chrome, 2014/01/30 00:22:56]

optional: consider using base::EqualsASCII for the first condition, and folding
the second and third into one call to base::LowerCaseEqualsASCII (unless "EN_*"
should be disallowed?)

[rpetterson, 2014/01/30 00:46:09]

That's correct. We only want the ones listed at this time, not ones like
"en-au".

+  if (group != "" && group != "Disabled" && locale_available) {

[asargent_no_longer_on_chrome, 2014/01/30 00:22:56]

optional: consider using 

  !group.empty() 

instead of 

  group != ""

Also, would it make sense to check the group first, and then only check the
locale if we're in the experiment group? I suppose the time to fetch and compare
the locale is pretty fast but this code runs on the startup path so early exits
anywhere we can get them help in aggregate. 

[rpetterson, 2014/01/30 00:46:09]

Done.

+    std::string hotwordId = extension_misc::kHotwordExtensionId;
+    prefs_->SetString(hotwordId + ".external_update_url",
+                      extension_urls::GetWebstoreUpdateUrl().spec());
+  }
+
   if (CommandLine::ForCurrentProcess()->
           GetSwitchValueASCII(switches::kEnableEnhancedBookmarks) != "0") {
     std::string ext_id = GetEnhancedBookmarksExtensionId();
     if (!ext_id.empty()) {
       prefs_->SetString(ext_id + ".external_update_url",
                         extension_urls::GetWebstoreUpdateUrl().spec());
     }
   }
 
 #if defined(OS_CHROMEOS)
@@ skipping 33 matching lines @@
 // static
 void ExternalComponentLoader::RegisterProfilePrefs(
     user_prefs::PrefRegistrySyncable* registry) {
 #if defined(OS_CHROMEOS)
   registry->RegisterListPref(prefs::kHighQualitySpeechSynthesisLanguages,
                              user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
 #endif
 }
 
 }  // namespace extensions