Fix issues and feature polishing for parallel download.

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 70 matching lines @@
   EXPECT_EQ(slice4, slices[1]);
 
   // A new slice can only merge with an existing slice earlier in the file, not
   // later in the file.
   DownloadItem::ReceivedSlice slice5(50, 50);
   EXPECT_EQ(0u, AddOrMergeReceivedSliceIntoSortedArray(slice5, slices));
   EXPECT_EQ(3u, slices.size());
   EXPECT_EQ(0, slices[0].offset);
   EXPECT_EQ(100, slices[0].received_bytes);
   EXPECT_EQ(slice4, slices[1]);
+}
 
+// Ensure the minimum slice size is correctly applied.
+TEST(ParallelDownloadUtilsTest, FindSlicesForRemainingContentMinSliceSize) {
+  // Minimum slice size is smaller than total length, only one slice returned.
+  DownloadItem::ReceivedSlices slices =
+      FindSlicesForRemainingContent(0, 100, 3, 150);
+  EXPECT_EQ(1u, slices.size());
+  EXPECT_EQ(0, slices[0].offset);
+  EXPECT_EQ(0, slices[0].received_bytes);
+
+  // Request count is large, the minimum slice size should limit the number of
+  // slices returned.
+  slices = FindSlicesForRemainingContent(0, 100, 33, 50);
+  EXPECT_EQ(2u, slices.size());
+  EXPECT_EQ(0, slices[0].offset);
+  EXPECT_EQ(50, slices[0].received_bytes);
+  EXPECT_EQ(50, slices[1].offset);
+  EXPECT_EQ(0, slices[1].received_bytes);
+
+  // Can chunk 2 slices under minimum slice size, but request count is only 1,
+  // request count should win.
+  slices = FindSlicesForRemainingContent(0, 100, 1, 50);
+  EXPECT_EQ(1u, slices.size());
+  EXPECT_EQ(0, slices[0].offset);
+  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);
 }
 
 }  // namespace content