[Downloads] Some UMA for downloads resumption.

content/browser/download/download_stats.cc

 // Copyright (c) 2012 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/download_stats.h"
 
 #include "base/metrics/histogram.h"
 #include "base/strings/string_util.h"
 #include "content/browser/download/download_resource_handler.h"
 #include "content/public/browser/download_interrupt_reasons.h"
@@ skipping 161 matching lines @@
   int max = 1024 * 1024;  // One Megabyte.
   UMA_HISTOGRAM_CUSTOM_COUNTS("Download.WriteSize", data_len, 1, max, 256);
 }
 
 void RecordDownloadWriteLoopCount(int count) {
   RecordDownloadCount(WRITE_LOOP_COUNT);
   UMA_HISTOGRAM_ENUMERATION("Download.WriteLoopCount", count, 20);
 }
 
 void RecordAcceptsRanges(const std::string& accepts_ranges,
-                         int64 download_len) {
+                         int64 download_len,
+                         const std::string& etag) {
   int64 max = 1024 * 1024 * 1024;  // One Terabyte.
   download_len /= 1024;  // In Kilobytes
   static const int kBuckets = 50;
 
   if (LowerCaseEqualsASCII(accepts_ranges, "none")) {
     UMA_HISTOGRAM_CUSTOM_COUNTS("Download.AcceptRangesNone.KBytes",
                                 download_len,
                                 1,
                                 max,
                                 kBuckets);
   } else if (LowerCaseEqualsASCII(accepts_ranges, "bytes")) {
     UMA_HISTOGRAM_CUSTOM_COUNTS("Download.AcceptRangesBytes.KBytes",
                                 download_len,
                                 1,
                                 max,
                                 kBuckets);
+    // ETags that start with "W/" are considered weak ETags which don't imply
+    // byte-wise equality.
+    if (!StartsWithASCII(etag, "w/", false))
+      RecordDownloadCount(STRONG_ETAG_AND_ACCEPTS_RANGES);
   } else {
     UMA_HISTOGRAM_CUSTOM_COUNTS("Download.AcceptRangesMissingOrInvalid.KBytes",
                                 download_len,
                                 1,
                                 max,
                                 kBuckets);
   }
 }
 
 namespace {
@@ skipping 241 matching lines @@
                            disk_write_time_ms * 100 / elapsed_time_ms);
 }
 
 void RecordSavePackageEvent(SavePackageEvent event) {
   UMA_HISTOGRAM_ENUMERATION("Download.SavePackage",
                             event,
                             SAVE_PACKAGE_LAST_ENTRY);
 }
 
 }  // namespace content