[MD Settings][People] Fixes take picture button disappearing on page refresh

BUG=660835

Review-Url: https://codereview.chromium.org/2480603003
Cr-Commit-Position: refs/heads/master@{#430272}

chrome/browser/ui/webui/settings/chromeos/change_picture_handler.cc

@@ -122,10 +122,14 @@ void ChangePictureHandler::OnJavascriptAllowed() {
                  content::NotificationService::AllSources());
   registrar_.Add(this, chrome::NOTIFICATION_LOGIN_USER_IMAGE_CHANGED,
                  content::NotificationService::AllSources());
+
+  camera_observer_.Add(CameraPresenceNotifier::GetInstance());
 }
 
 void ChangePictureHandler::OnJavascriptDisallowed() {
   registrar_.RemoveAll();
+
+  camera_observer_.Remove(CameraPresenceNotifier::GetInstance());
 }
 
 void ChangePictureHandler::SendDefaultImages() {
@@ -204,10 +208,6 @@ void ChangePictureHandler::HandlePageInitialized(const base::ListValue* args) {
 
   AllowJavascript();
 
-  CameraPresenceNotifier* camera = CameraPresenceNotifier::GetInstance();
-  if (!camera_observer_.IsObserving(camera))
-    camera_observer_.Add(camera);
-
   SendDefaultImages();
   SendSelectedImage();
   UpdateProfileImage();