Migrate callers of message_loop_proxy() to task_runner()

sync/internal_api/attachments/attachment_downloader_impl_unittest.cc

Index: sync/internal_api/attachments/attachment_downloader_impl_unittest.cc
diff --git a/sync/internal_api/attachments/attachment_downloader_impl_unittest.cc b/sync/internal_api/attachments/attachment_downloader_impl_unittest.cc
index 0cae099337e11942ea598066ca02b2dd5676ceea..9cf16b4ee1f28ec0ddf127706fb72cc244f1c91f 100644
--- a/sync/internal_api/attachments/attachment_downloader_impl_unittest.cc
+++ b/sync/internal_api/attachments/attachment_downloader_impl_unittest.cc
@@ -205,7 +205,7 @@ class AttachmentDownloaderImplTest : public testing::Test {
 
 void AttachmentDownloaderImplTest::SetUp() {
   url_request_context_getter_ =
-      new net::TestURLRequestContextGetter(message_loop_.message_loop_proxy());
+      new net::TestURLRequestContextGetter(message_loop_.task_runner());
   url_fetcher_factory_.set_remove_fetcher_on_delete(true);
   token_service_.reset(new MockOAuth2TokenService());
   token_service_->AddAccount(kAccountId);