Always load signin profile on Chrome OS startup.

chrome/browser/extensions/api/file_system/file_system_apitest_chromeos.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/path_service.h"
 #include "chrome/browser/apps/app_browsertest_util.h"
 #include "chrome/browser/chromeos/drive/drive_integration_service.h"
 #include "chrome/browser/chromeos/drive/file_system_interface.h"
 #include "chrome/browser/chromeos/drive/file_system_util.h"
+#include "chrome/browser/chromeos/profiles/profile_helper.h"
 #include "chrome/browser/drive/fake_drive_service.h"
 #include "chrome/browser/extensions/api/file_system/file_system_api.h"
 #include "chrome/browser/extensions/component_loader.h"
 #include "chrome/common/chrome_paths.h"
 #include "content/public/test/test_utils.h"
 #include "google_apis/drive/drive_api_parser.h"
 #include "google_apis/drive/test_util.h"
 
 namespace extensions {
 
@@ skipping 37 matching lines @@
   }
 
   void TearDown() override {
     FileSystemChooseEntryFunction::StopSkippingPickerForTest();
     PlatformAppBrowserTest::TearDown();
   };
 
  private:
   drive::DriveIntegrationService* CreateDriveIntegrationService(
       Profile* profile) {
+    // Ignore signin profile.
+    if (profile->GetPath() == chromeos::ProfileHelper::GetSigninProfileDir())
+      return NULL;
+
+    // FileSystemApiTestForDrive doesn't expect that several user profiles could
+    // exist simultaneously.
+    CHECK(fake_drive_service_ == NULL);
     fake_drive_service_ = new drive::FakeDriveService;
     fake_drive_service_->LoadAppListForDriveApi("drive/applist.json");
 
     SetUpTestFileHierarchy();
 
     integration_service_ = new drive::DriveIntegrationService(
         profile, NULL, fake_drive_service_, std::string(),
         test_cache_root_.path(), NULL);
     return integration_service_;
   }
@@ skipping 170 matching lines @@
     FileSystemApiSaveExistingFileWithWriteTest) {
   base::FilePath test_file = drive::util::GetDriveMountPointPath(
       browser()->profile()).AppendASCII("root/save_existing.txt");
   FileSystemChooseEntryFunction::SkipPickerAndAlwaysSelectPathForTest(
       &test_file);
   ASSERT_TRUE(RunPlatformAppTest(
       "api_test/file_system/save_existing_with_write")) << message_;
 }
 
 }  // namespace extensions