Use ByteStream in downloads system to decouple source and sink.

content/browser/download/download_stats.cc

Index: content/browser/download/download_stats.cc
diff --git a/content/browser/download/download_stats.cc b/content/browser/download/download_stats.cc
index 40ed9123d8ebf4fcf09a9da2b998fbd8346158bc..ce066d6dda12821837fa42cfd38fc8c276821009 100644
--- a/content/browser/download/download_stats.cc
+++ b/content/browser/download/download_stats.cc
@@ -255,8 +255,7 @@ void RecordDownloadMimeType(const std::string& mime_type_string) {
 void RecordFileThreadReceiveBuffers(size_t num_buffers) {
     UMA_HISTOGRAM_CUSTOM_COUNTS(
       "Download.FileThreadReceiveBuffers", num_buffers, 1,
-      DownloadResourceHandler::kLoadsToWrite,
-      DownloadResourceHandler::kLoadsToWrite);
+      100, 100);
 }
 
 void RecordBandwidth(double actual_bandwidth, double potential_bandwidth) {
@@ -303,6 +302,43 @@ void RecordOpensOutstanding(int size) {
                               64/*num_buckets*/);
 }
 
+void RecordContiguousWriteTime(base::TimeDelta time_blocked) {
+  UMA_HISTOGRAM_TIMES("Download.FileThreadBlockedTime", time_blocked);
+}
+
+void RecordNetworkBandwidth(size_t length,
+                            base::TimeDelta elapsed_time,
+                            base::TimeDelta paused_time) {
+  size_t non_pause_time_ms = (elapsed_time - paused_time).InMilliseconds();
+  if (0u == non_pause_time_ms)
+    non_pause_time_ms = 1;
+
+  // Note that this will be somewhat higher than sustainable network
+  // bandwidth because of buffering in the kernel during pauses.
+  UMA_HISTOGRAM_CUSTOM_COUNTS(
+      "Download.BandwidthNetwork",

[benjhayden, 2012/05/30 20:22:33]

Include units (looks like Bps?) in case you decide to add bps or KBps?
Also, network bandwidth is usually bits-per-second rather than bytes, so it
would be good to at least comment that you're breaking tradition.

+      (1000 * length / non_pause_time_ms),
+      1, 100000000, 50);
+}
+
+void RecordFileBandwidth(size_t length,
+                         base::TimeDelta disk_write_time,
+                         base::TimeDelta elapsed_time) {
+  size_t elapsed_time_ms = elapsed_time.InMilliseconds();
+  if (0u == elapsed_time_ms)
+    elapsed_time_ms = 1;
+  size_t disk_write_time_ms = disk_write_time.InMilliseconds();
+  if (0u == disk_write_time_ms)
+    disk_write_time_ms = 1;
+
+  UMA_HISTOGRAM_CUSTOM_COUNTS(
+      "Download.BandwidthOverall",
+      (1000 * length / elapsed_time_ms), 1, 50000000, 50);
+  UMA_HISTOGRAM_CUSTOM_COUNTS(
+      "Download.BandwidthDisk",
+      (1000 * length / disk_write_time_ms), 1, 50000000, 50);
+}
+
 void RecordSavePackageEvent(SavePackageEvent event) {
   UMA_HISTOGRAM_ENUMERATION("Download.SavePackage",
                             event,