Properly handle the case when a parallel download becomes non-parallel

content/browser/download/parallel_download_utils_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 "content/browser/download/parallel_download_utils.h"
 
 #include "content/public/browser/download_save_info.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace content {
@@ skipping 105 matching lines @@
   EXPECT_EQ(0, slices[0].received_bytes);
 
   // A total 100 bytes data and a 51 bytes minimum slice size, only one slice is
   // returned.
   slices = FindSlicesForRemainingContent(0, 100, 3, 51);
   EXPECT_EQ(1u, slices.size());
   EXPECT_EQ(0, slices[0].offset);
   EXPECT_EQ(0, slices[0].received_bytes);
 }
 
+TEST(ParallelDownloadUtilsTest, GetMaxContiguousDataBlockSizeFromBeginning) {
+  std::vector<DownloadItem::ReceivedSlice> slices;
+  slices.emplace_back(500, 500);
+  EXPECT_EQ(0, GetMaxContiguousDataBlockSizeFromBeginning(slices));
+
+  DownloadItem::ReceivedSlice slice1(0, 200);
+  AddOrMergeReceivedSliceIntoSortedArray(slice1, slices);
+  EXPECT_EQ(200, GetMaxContiguousDataBlockSizeFromBeginning(slices));
+
+  DownloadItem::ReceivedSlice slice2(200, 300);
+  AddOrMergeReceivedSliceIntoSortedArray(slice2, slices);
+  EXPECT_EQ(1000, GetMaxContiguousDataBlockSizeFromBeginning(slices));
+}
+
 }  // namespace content