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 <map>
 #include <string>
 #include <utility>
 
@@ skipping 452 matching lines @@
 
   service.Flush();
   EXPECT_EQ(1, GetPersistedLogCount());
 
   auto proto_report = GetPersistedReport();
   // Note, 2 instead of 3 sources, since we overrode the max number of sources
   // via Feature params.
   EXPECT_EQ(2, proto_report.sources_size());
 }
 
+TEST_F(UkmServiceTest, PurgeMidUpload) {
+  UkmService service(&prefs_, &client_);
+  EXPECT_EQ(GetPersistedLogCount(), 0);
+  service.Initialize();
+  task_runner_->RunUntilIdle();
+  service.EnableRecording();
+  service.EnableReporting();
+  auto id = UkmService::GetNewSourceID();
+  service.UpdateSourceURL(id, GURL("https://google.com/foobar1"));
+  // 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