Change AboutResourceLoader::GetAboutResource to wait for inflight update task.

chrome/browser/chromeos/drive/change_list_loader_unittest.cc

Index: chrome/browser/chromeos/drive/change_list_loader_unittest.cc
diff --git a/chrome/browser/chromeos/drive/change_list_loader_unittest.cc b/chrome/browser/chromeos/drive/change_list_loader_unittest.cc
index d6e1c32b75555f6616ef388880c5973ae8852db9..ea639b8bc612b2aa1fe33a333885c7cda61f7ae6 100644
--- a/chrome/browser/chromeos/drive/change_list_loader_unittest.cc
+++ b/chrome/browser/chromeos/drive/change_list_loader_unittest.cc
@@ -143,6 +143,70 @@ class ChangeListLoaderTest : public testing::Test {
   scoped_ptr<ChangeListLoader> change_list_loader_;
 };
 
+TEST_F(ChangeListLoaderTest, AboutResourceLoader) {
+  google_apis::GDataErrorCode error[6] = {};
+  scoped_ptr<google_apis::AboutResource> about[6];
+
+  // No resource is cached at the beginning.
+  ASSERT_FALSE(about_resource_loader_->cached_about_resource());
+
+  // Since no resource is cached, this "Get" should trigger the update.
+  about_resource_loader_->GetAboutResource(
+      google_apis::test_util::CreateCopyResultCallback(error + 0, about + 0));
+  // Since there is one in-flight update, the next "Get" just wait for it.
+  about_resource_loader_->GetAboutResource(
+      google_apis::test_util::CreateCopyResultCallback(error + 1, about + 1));
+
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(google_apis::HTTP_SUCCESS, error[0]);
+  EXPECT_EQ(google_apis::HTTP_SUCCESS, error[1]);
+  const int64 first_changestamp = about[0]->largest_change_id();
+  EXPECT_EQ(first_changestamp, about[1]->largest_change_id());
+  ASSERT_TRUE(about_resource_loader_->cached_about_resource());
+  EXPECT_EQ(
+      first_changestamp,
+      about_resource_loader_->cached_about_resource()->largest_change_id());
+
+  // Increment changestamp by 1.
+  AddNewFile("temp");
+  // Explicitly calling UpdateAboutResource will start another API call.
+  about_resource_loader_->UpdateAboutResource(
+      google_apis::test_util::CreateCopyResultCallback(error + 2, about + 2));
+  // It again waits for the in-flight UpdateAboutResoure call, even though this
+  // time there is a cached result.
+  about_resource_loader_->GetAboutResource(
+      google_apis::test_util::CreateCopyResultCallback(error + 3, about + 3));
+
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(google_apis::HTTP_SUCCESS, error[2]);
+  EXPECT_EQ(google_apis::HTTP_SUCCESS, error[3]);
+  EXPECT_EQ(first_changestamp + 1, about[2]->largest_change_id());
+  EXPECT_EQ(first_changestamp + 1, about[3]->largest_change_id());
+  EXPECT_EQ(
+      first_changestamp + 1,
+      about_resource_loader_->cached_about_resource()->largest_change_id());
+
+  // Increment changestamp by 1.
+  AddNewFile("temp2");
+  // Now no UpdateAboutResource task is running. Returns the cached result.
+  about_resource_loader_->GetAboutResource(
+      google_apis::test_util::CreateCopyResultCallback(error + 4, about + 4));
+  // Explicitly calling UpdateAboutResource will start another API call.
+  about_resource_loader_->UpdateAboutResource(
+      google_apis::test_util::CreateCopyResultCallback(error + 5, about + 5));
+
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(google_apis::HTTP_NO_CONTENT, error[4]);
+  EXPECT_EQ(google_apis::HTTP_SUCCESS, error[5]);
+  EXPECT_EQ(first_changestamp + 1, about[4]->largest_change_id());
+  EXPECT_EQ(first_changestamp + 2, about[5]->largest_change_id());
+  EXPECT_EQ(
+      first_changestamp + 2,
+      about_resource_loader_->cached_about_resource()->largest_change_id());
+
+  EXPECT_EQ(3, drive_service_->about_resource_load_count());
+}
+
 TEST_F(ChangeListLoaderTest, Load) {
   EXPECT_FALSE(change_list_loader_->IsRefreshing());