Add UMA metric to track parallel download requests stats.

content/browser/download/parallel_download_job.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_job.h"
 
 #include "base/memory/ptr_util.h"
 #include "content/browser/download/download_create_info.h"
+#include "content/browser/download/download_stats.h"
 #include "content/browser/download/parallel_download_utils.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/storage_partition.h"
 
 namespace content {
 namespace {
 
 const int kVerboseLevel = 1;
 
 }  // namespace
@@ skipping 76 matching lines @@
 
   timer_.Start(FROM_HERE, GetParallelRequestDelayConfig(), this,
                &ParallelDownloadJob::BuildParallelRequests);
 }
 
 void ParallelDownloadJob::OnByteStreamReady(
     DownloadWorker* worker,
     std::unique_ptr<ByteStreamReader> stream_reader) {
   bool success = DownloadJob::AddByteStream(std::move(stream_reader),
                                             worker->offset(), worker->length());
+  RecordParallelDownloadAddStreamSuccess(success);
 
   // Destroy the request if the sink is gone.
   if (!success) {
     VLOG(kVerboseLevel)
         << "Byte stream arrived after download file is released.";
     worker->Cancel();
   }
 }
 
 void ParallelDownloadJob::OnServerResponseError(
@@ skipping 48 matching lines @@
   DCHECK_EQ(slices_to_download.back().received_bytes,
             DownloadSaveInfo::kLengthFullContent);
 
   ForkSubRequests(slices_to_download);
   requests_sent_ = true;
 }
 
 void ParallelDownloadJob::ForkSubRequests(
     const DownloadItem::ReceivedSlices& slices_to_download) {
   bool initial_request_skipped = false;
+  int requests_num = 0;
+  int early_requests_num = 0;
+
   for (auto it = slices_to_download.begin(); it != slices_to_download.end();
        ++it) {
     // Create requests for holes before the |initial_request_offset_|.
     if (it->offset < initial_request_offset_) {
       CreateRequest(it->offset, it->received_bytes);
+      early_requests_num++;
+      requests_num++;
       continue;
     }
 
     // Assume the first slice to download after |initial_request_offset_| will
     // be handled by the initial request.
-    if (initial_request_skipped)
+    if (initial_request_skipped) {
       CreateRequest(it->offset, it->received_bytes);
-    else
+      requests_num++;
+    } else
       initial_request_skipped = true;
   }
+
+  RecordParallelDownloadRequestCount(requests_num + 1);
+  if (early_requests_num > 0)
+    RecordParallelDownloadEarlyRequests(early_requests_num);
 }
 
 void ParallelDownloadJob::CreateRequest(int64_t offset, int64_t length) {
   DCHECK(download_item_);
 
   std::unique_ptr<DownloadWorker> worker =
       base::MakeUnique<DownloadWorker>(this, offset, length);
 
   StoragePartition* storage_partition =
       BrowserContext::GetStoragePartitionForSite(
@@ skipping 15 matching lines @@
   // download request.
   download_params->set_referrer(Referrer(download_item_->GetReferrerUrl(),
                                          blink::WebReferrerPolicyAlways));
   // Send the request.
   worker->SendRequest(std::move(download_params));
   DCHECK(workers_.find(offset) == workers_.end());
   workers_[offset] = std::move(worker);
 }
 
 }  // namespace content