Handle the case where Purge is called while upload is in progress.

components/ukm/ukm_service_unittest.cc

 // Copyright 2017 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 "components/ukm/ukm_service.h"
 
 #include <string>
 #include <utility>
 
 #include "base/test/test_simple_task_runner.h"
@@ skipping 170 matching lines @@
   service.RecordSource(MakeSource("https://google.com", 300));
   // Includes a Source, so will persist.
   service.Flush();
   EXPECT_EQ(GetPersistedLogCount(), 1);
 
   // Current log has no Sources.
   service.Flush();
   EXPECT_EQ(GetPersistedLogCount(), 1);
 }
 
+TEST_F(UkmServiceTest, PurgeMidUpload) {
+  UkmService service(&prefs_, &client_);
+  EXPECT_EQ(GetPersistedLogCount(), 0);
+  service.Initialize();
+  task_runner_->RunUntilIdle();
+  service.EnableRecording();
+  service.EnableReporting();
+  service.RecordSource(MakeSource("https://google.com", 300));
+  // Should init, generate a log, and start an upload.
+  task_runner_->RunPendingTasks();
+  EXPECT_TRUE(client_.uploader()->is_uploading());
+  // Purge should delete all logs, including the one being sent.
+  service.Purge();
+  // Upload succeeds after logs was deleted.
+  client_.uploader()->CompleteUpload(200);
+  EXPECT_EQ(GetPersistedLogCount(), 0);
+  EXPECT_FALSE(client_.uploader()->is_uploading());
+}
+
 }  // namespace ukm