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

content/browser/download/parallel_download_utils_unittest.cc

Index: content/browser/download/parallel_download_utils_unittest.cc
diff --git a/content/browser/download/parallel_download_utils_unittest.cc b/content/browser/download/parallel_download_utils_unittest.cc
index eab9d3801cabd7961a2329632622955e4a1948c8..0d7cad92b86f11adf2a5e2110afba3dfed645b86 100644
--- a/content/browser/download/parallel_download_utils_unittest.cc
+++ b/content/browser/download/parallel_download_utils_unittest.cc
@@ -123,4 +123,18 @@ TEST(ParallelDownloadUtilsTest, FindSlicesForRemainingContentMinSliceSize) {
   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