Open the launcher when hotword is triggered in always-on mode.

chrome/browser/extensions/api/hotword_private/hotword_private_api.cc

Index: chrome/browser/extensions/api/hotword_private/hotword_private_api.cc
diff --git a/chrome/browser/extensions/api/hotword_private/hotword_private_api.cc b/chrome/browser/extensions/api/hotword_private/hotword_private_api.cc
index 2de65c89c42932bd1e8bd662cb6944e222dbd711..db6db77b3068dfbd8c683b616104c4a280f135c9 100644
--- a/chrome/browser/extensions/api/hotword_private/hotword_private_api.cc
+++ b/chrome/browser/extensions/api/hotword_private/hotword_private_api.cc
@@ -11,6 +11,7 @@
 #include "chrome/browser/search/hotword_client.h"
 #include "chrome/browser/search/hotword_service.h"
 #include "chrome/browser/search/hotword_service_factory.h"
+#include "chrome/browser/ui/app_list/app_list_service.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
 #include "extensions/browser/event_router.h"
@@ -157,8 +158,17 @@ bool HotwordPrivateSetHotwordSessionStateFunction::RunSync() {
 bool HotwordPrivateNotifyHotwordRecognitionFunction::RunSync() {
   HotwordService* hotword_service =
       HotwordServiceFactory::GetForProfile(GetProfile());
-  if (hotword_service && hotword_service->client())
-    hotword_service->client()->OnHotwordRecognized();
+  if (hotword_service) {
+    if (hotword_service->client()) {
+      hotword_service->client()->OnHotwordRecognized();
+    } else if (HotwordService::IsExperimentalHotwordingEnabled() &&
+               hotword_service->IsAlwaysOnEnabled()) {
+      AppListService* app_list_service = AppListService::Get(
+          chrome::HOST_DESKTOP_TYPE_NATIVE);

[tapted, 2014/10/09 03:37:00]

you might want AppListService::Get(GetCurrentBrowser()->host_desktop_type()); 
Or, if this can be called when there are no browser windows open,
chrome::GetActiveDesktop().

Otherwise, if the user is in Metro mode on Windows 8 and this triggers, it will
show the app launcher on the Windows 8 desktop, which they won't see.

[Anand Mistry (off Chromium), 2014/10/13 21:51:59]

Done. But note, priority is ChromeOS. We're not targeting Windows 8 (or Linux,
or OSX).

+      CHECK(app_list_service);
+      app_list_service->ShowForVoiceSearch(GetProfile());
+    }
+  }
   return true;
 }