Update the received slices vector when stream is written to disk

content/browser/download/parallel_download_utils.cc

Index: content/browser/download/parallel_download_utils.cc
diff --git a/content/browser/download/parallel_download_utils.cc b/content/browser/download/parallel_download_utils.cc
index d21ea49f20c061e15a062e6fec4758ea0e905705..5bd4413c9628aaa6cb4e5ed3f6428919ae1613fd 100644
--- a/content/browser/download/parallel_download_utils.cc
+++ b/content/browser/download/parallel_download_utils.cc
@@ -28,6 +28,13 @@ const char kParallelRequestCountFinchKey[] = "request_count";
 // specified.
 const int kParallelRequestCount = 2;
 
+// TODO(qinmin): replace this with a comparator operator in
+// DownloadItem::ReceivedSlice.
+bool compareReceivedSlices(const DownloadItem::ReceivedSlice& lhs,
+                           const DownloadItem::ReceivedSlice& rhs) {
+  return lhs.offset < rhs.offset;
+}
+
 }  // namespace
 
 std::vector<DownloadItem::ReceivedSlice> FindSlicesToDownload(
@@ -61,6 +68,24 @@ std::vector<DownloadItem::ReceivedSlice> FindSlicesToDownload(
   return result;
 }
 
+size_t AddOrMergeReceivedSliceIntoSortedArray(
+    const DownloadItem::ReceivedSlice& new_slice,
+    std::vector<DownloadItem::ReceivedSlice>& received_slices) {
+  std::vector<DownloadItem::ReceivedSlice>::iterator it =
+      std::upper_bound(received_slices.begin(), received_slices.end(),
+                       new_slice, compareReceivedSlices);
+  if (it != received_slices.begin()) {
+    std::vector<DownloadItem::ReceivedSlice>::iterator prev = std::prev(it);
+    if (prev->offset + prev->received_bytes == new_slice.offset) {
+      prev->received_bytes += new_slice.received_bytes;
+      return static_cast<size_t>(std::distance(received_slices.begin(), prev));
+    }
+  }
+
+  it = received_slices.emplace(it, new_slice);
+  return static_cast<size_t>(std::distance(received_slices.begin(), it));
+}
+
 int64_t GetMinSliceSizeConfig() {
   std::string finch_value = base::GetFieldTrialParamValueByFeature(
       features::kParallelDownloading, kMinSliceSizeFinchKey);