Always load signin profile on Chrome OS startup.

chrome/browser/chromeos/file_manager/external_filesystem_apitest.cc

Index: chrome/browser/chromeos/file_manager/external_filesystem_apitest.cc
diff --git a/chrome/browser/chromeos/file_manager/external_filesystem_apitest.cc b/chrome/browser/chromeos/file_manager/external_filesystem_apitest.cc
index c93c6d7d464b8c0cfd7e60a135846112862ff81a..1eab05a8e329609fad484f62a2ff8b9fdc3b8597 100644
--- a/chrome/browser/chromeos/file_manager/external_filesystem_apitest.cc
+++ b/chrome/browser/chromeos/file_manager/external_filesystem_apitest.cc
@@ -529,6 +529,13 @@ class DriveFileSystemExtensionApiTest : public FileSystemExtensionApiTestBase {
   // DriveIntegrationService factory function for this test.
   drive::DriveIntegrationService* CreateDriveIntegrationService(
       Profile* profile) {
+    // Ignore signin profile.
+    if (profile->GetPath() == chromeos::ProfileHelper::GetSigninProfileDir())
+      return NULL;
+
+    // DriveFileSystemExtensionApiTest doesn't expect that several user profiles
+    // could exist simultaneously.
+    DCHECK(fake_drive_service_ == NULL);
     fake_drive_service_ = new drive::FakeDriveService;
     fake_drive_service_->LoadAppListForDriveApi("drive/applist.json");