Use mojo volume interfaces for mash and classic ash.

chrome/browser/chromeos/chrome_browser_main_chromeos.cc

Index: chrome/browser/chromeos/chrome_browser_main_chromeos.cc
diff --git a/chrome/browser/chromeos/chrome_browser_main_chromeos.cc b/chrome/browser/chromeos/chrome_browser_main_chromeos.cc
index 6fd01a40014b7e239c46d458cea2c905f8559487..d8f70245e21d0b9652c44b8417ce1eaa5e20bf5a 100644
--- a/chrome/browser/chromeos/chrome_browser_main_chromeos.cc
+++ b/chrome/browser/chromeos/chrome_browser_main_chromeos.cc
@@ -45,6 +45,7 @@
 #include "chrome/browser/chromeos/events/event_rewriter_controller.h"
 #include "chrome/browser/chromeos/events/keyboard_driven_event_rewriter.h"
 #include "chrome/browser/chromeos/extensions/default_app_order.h"
+#include "chrome/browser/chromeos/extensions/extension_system_event_observer.h"
 #include "chrome/browser/chromeos/external_metrics.h"
 #include "chrome/browser/chromeos/input_method/input_method_configuration.h"
 #include "chrome/browser/chromeos/input_method/input_method_util.h"
@@ -670,6 +671,9 @@ void ChromeBrowserMainPartsChromeos::PostProfileInit() {
   if (user_manager::UserManager::Get()->IsLoggedInAsGuest())
     SetGuestLocale(profile());
 
+  // This observer uses the intialized profile to dispatch extension events.
+  extension_system_event_observer_.reset(new ExtensionSystemEventObserver());

[sky, 2016/10/20 15:41:07]

MakeUnique if you can.

[msw, 2016/10/20 16:15:32]

Done here and elsewhere in this function.

+
   peripheral_battery_observer_.reset(new PeripheralBatteryObserver());
 
   renderer_freezer_.reset(
@@ -798,6 +802,7 @@ void ChromeBrowserMainPartsChromeos::PostMainMessageLoopRun() {
 
   // We should remove observers attached to D-Bus clients before
   // DBusThreadManager is shut down.
+  extension_system_event_observer_.reset();
   peripheral_battery_observer_.reset();
   power_prefs_.reset();
   renderer_freezer_.reset();