Adds HotwordPrivate API for integrating the hotword feature to AppLauncher

chrome/browser/ui/webui/app_list/start_page_handler.cc

Index: chrome/browser/ui/webui/app_list/start_page_handler.cc
diff --git a/chrome/browser/ui/webui/app_list/start_page_handler.cc b/chrome/browser/ui/webui/app_list/start_page_handler.cc
index 930b75b2d099d6e2ac7386cb394be20c1cb4df31..604797357880b2729621a8b9ab7a29347ec499ac 100644
--- a/chrome/browser/ui/webui/app_list/start_page_handler.cc
+++ b/chrome/browser/ui/webui/app_list/start_page_handler.cc
@@ -35,6 +35,10 @@ namespace app_list {
 
 namespace {
 
+#if defined(OS_CHROMEOS)
+const char kOldHotwordExtensionVersionString[] = "0.1.1.5014_0";
+#endif
+
 scoped_ptr<base::DictionaryValue> CreateAppInfo(
     const extensions::Extension* app) {
   scoped_ptr<base::DictionaryValue> dict(new base::DictionaryValue);
@@ -131,11 +135,25 @@ void StartPageHandler::SendRecommendedApps() {
 
 #if defined(OS_CHROMEOS)
 void StartPageHandler::OnHotwordEnabledChanged() {
-  StartPageService* service = StartPageService::Get(
-      Profile::FromWebUI(web_ui()));
-  web_ui()->CallJavascriptFunction(
-      "appList.startPage.setHotwordEnabled",
-      base::FundamentalValue(service->HotwordEnabled()));
+  // If the hotword extension is new enough, we should use the new
+  // hotwordPrivate API to provide the feature.
+  // TODO(mukai): remove this after everything gets stable.
+  Profile* profile = Profile::FromWebUI(web_ui());
+  ExtensionService* extension_service =
+      extensions::ExtensionSystem::Get(profile)->extension_service();
+  if (!extension_service)
+    return;
+
+  const extensions::Extension* hotword_extension =
+      extension_service->GetExtensionById(
+          extension_misc::kHotwordExtensionId, false /* include_disabled */);
+  if (hotword_extension && hotword_extension->version()->CompareTo(
+          base::Version(kOldHotwordExtensionVersionString)) <= 0) {
+    StartPageService* service = StartPageService::Get(profile);
+    web_ui()->CallJavascriptFunction(
+        "appList.startPage.setHotwordEnabled",
+        base::FundamentalValue(service->HotwordEnabled()));
+  }
 }
 #endif