Isolate initiation counts for downloads to their own histograms and improve

chrome/browser/download/download_resource_throttle.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 "chrome/browser/download/download_resource_throttle.h"
 
 #include "base/bind.h"
+#include "chrome/browser/download/download_util.h"
 #include "content/public/browser/resource_throttle_controller.h"
 
 DownloadResourceThrottle::DownloadResourceThrottle(
     DownloadRequestLimiter* limiter,
     int render_process_id,
     int render_view_id,
     int request_id)
     : request_allowed_(false),
       request_deferred_(false) {
   limiter->CanDownloadOnIOThread(
@@ skipping 15 matching lines @@
                                                    bool* defer) {
   *defer = request_deferred_ = !request_allowed_;
 }
 
 void DownloadResourceThrottle::WillProcessResponse(bool* defer) {
   *defer = request_deferred_ = !request_allowed_;
 }
 
 void DownloadResourceThrottle::ContinueDownload(bool allow) {
   request_allowed_ = allow;
+  if (allow) {
+    // Presumes all downloads initiated by navigation using this throttle and
+    // nothing else does.
+    download_util::RecordDownloadSource(
+        download_util::INITIATED_BY_NAVIGATION);
+  } else {
+    download_util::RecordDownloadCount(download_util::BLOCKED_BY_THROTTLING);
+  }
 
   if (request_deferred_) {
     if (allow) {
       controller()->Resume();
     } else {
       controller()->Cancel();
     }
   }
 }