Add UMA for estimating disk bandwidth and the time saved with parallel download

content/browser/download/download_item_impl.cc

Index: content/browser/download/download_item_impl.cc
diff --git a/content/browser/download/download_item_impl.cc b/content/browser/download/download_item_impl.cc
index f118a476be598052f23acd1ffe392e303b084e39..0ea6618a5e5e5f9ffaf17da6677a2247871f56ae 100644
--- a/content/browser/download/download_item_impl.cc
+++ b/content/browser/download/download_item_impl.cc
@@ -378,6 +378,13 @@ void DownloadItemImpl::Pause() {
     case TARGET_PENDING_INTERNAL:
       job_->Pause();
       UpdateObservers();
+      if (download_file_) {
+        BrowserThread::PostTask(
+            BrowserThread::FILE, FROM_HERE,
+            base::Bind(&DownloadFile::Pause,
+                       // Safe because we control download file lifetime.
+                       base::Unretained(download_file_.get())));
+      }
       return;
 
     case MAX_DOWNLOAD_INTERNAL_STATE: