settings: Make DeviceOAuth2TokenServiceFactory::Get() async

chrome/browser/ui/webui/print_preview/print_preview_handler.cc

Index: chrome/browser/ui/webui/print_preview/print_preview_handler.cc
diff --git a/chrome/browser/ui/webui/print_preview/print_preview_handler.cc b/chrome/browser/ui/webui/print_preview/print_preview_handler.cc
index 962e93b6c22268f7fbad69e4d51a769535f05cc6..45509d696ce225df084c681ab58e137af4a3d826 100644
--- a/chrome/browser/ui/webui/print_preview/print_preview_handler.cc
+++ b/chrome/browser/ui/webui/print_preview/print_preview_handler.cc
@@ -373,7 +373,8 @@ class PrintPreviewHandler::AccessTokenService
     : public OAuth2TokenService::Consumer {
  public:
   explicit AccessTokenService(PrintPreviewHandler* handler)
-      : handler_(handler) {
+      : handler_(handler),
+        weak_factory_(this) {
   }
 
   void RequestToken(const std::string& type) {
@@ -392,13 +393,35 @@ class PrintPreviewHandler::AccessTokenService
       }
     } else if (type == "device") {
 #if defined(OS_CHROMEOS)
-      chromeos::DeviceOAuth2TokenService* token_service =
-          chromeos::DeviceOAuth2TokenServiceFactory::Get();
-      account_id = token_service->GetRobotAccountId();
-      service = token_service;
+      chromeos::DeviceOAuth2TokenServiceFactory::Get(
+          base::Bind(
+              &AccessTokenService::DidGetTokenService,
+              weak_factory_.GetWeakPtr(),
+              type));
+      return;
 #endif
     }
 
+    ContinueRequestToken(type, service, account_id);
+  }
+
+#if defined(OS_CHROMEOS)
+  // Continuation of RequestToken().
+  void DidGetTokenService(const std::string& type,
+                          chromeos::DeviceOAuth2TokenService* token_service) {
+    std::string account_id;
+    if (token_service)
+      account_id = token_service->GetRobotAccountId();
+    ContinueRequestToken(type,
+                         token_service,
+                         account_id);
+  }
+#endif
+
+  // Continuation of RequestToken().
+  void ContinueRequestToken(const std::string& type,
+                            OAuth2TokenService* service,
+                            const std::string& account_id) {
     if (service) {
       OAuth2TokenService::ScopeSet oauth_scopes;
       oauth_scopes.insert(cloud_print::kCloudPrintAuth);
@@ -438,6 +461,7 @@ class PrintPreviewHandler::AccessTokenService
                    linked_ptr<OAuth2TokenService::Request> > Requests;
   Requests requests_;
   PrintPreviewHandler* handler_;
+  base::WeakPtrFactory<AccessTokenService> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(AccessTokenService);
 };