Always load signin profile on Chrome OS startup.

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

Index: chrome/browser/extensions/api/file_system/file_system_apitest_chromeos.cc
diff --git a/chrome/browser/extensions/api/file_system/file_system_apitest_chromeos.cc b/chrome/browser/extensions/api/file_system/file_system_apitest_chromeos.cc
index b6e67fa31a8c7733d284268f7807f4356891243e..7ae0d439c8de1debeb7a1a841f601a8da7a58813 100644
--- a/chrome/browser/extensions/api/file_system/file_system_apitest_chromeos.cc
+++ b/chrome/browser/extensions/api/file_system/file_system_apitest_chromeos.cc
@@ -7,11 +7,13 @@
 #include "chrome/browser/chromeos/drive/file_system_interface.h"
 #include "chrome/browser/chromeos/drive/file_system_util.h"
 #include "chrome/browser/chromeos/drive/test_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 "content/public/test/test_utils.h"
 #include "google_apis/drive/test_util.h"
 
+
 namespace extensions {
 
 // This class contains chrome.filesystem API test specific to Chrome OS, namely,
@@ -60,6 +62,13 @@ class FileSystemApiTestForDrive : public PlatformAppBrowserTest {
  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");