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

chrome/browser/extensions/external_component_loader.cc

Index: chrome/browser/extensions/external_component_loader.cc
diff --git a/chrome/browser/extensions/external_component_loader.cc b/chrome/browser/extensions/external_component_loader.cc
index ecfc18bd44fc9a0558e92dbc6f11fa79f8c52fa4..9d354467fab55d7ccedfcc2a0ac462f904faf5aa 100644
--- a/chrome/browser/extensions/external_component_loader.cc
+++ b/chrome/browser/extensions/external_component_loader.cc
@@ -5,6 +5,8 @@
 #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"
@@ -16,6 +18,7 @@
 #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 {
 
@@ -58,6 +61,26 @@ void ExternalComponentLoader::StartLoading() {
   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();