Add new UMA stats to get a handle on Downloads UI Usage

content/browser/download/download_manager.cc

Index: content/browser/download/download_manager.cc
diff --git a/content/browser/download/download_manager.cc b/content/browser/download/download_manager.cc
index e3235aea22fd6ecfb8f37603ce14f577d2ef4352..14248d82831da79154d5c7f8df88796af1f15c3d 100644
--- a/content/browser/download/download_manager.cc
+++ b/content/browser/download/download_manager.cc
@@ -25,6 +25,7 @@
 #include "content/browser/download/download_item.h"
 #include "content/browser/download/download_manager_delegate.h"
 #include "content/browser/download/download_persistent_store_info.h"
+#include "content/browser/download/download_stats.h"
 #include "content/browser/download/download_status_updater.h"
 #include "content/browser/renderer_host/render_process_host.h"
 #include "content/browser/renderer_host/render_view_host.h"
@@ -326,6 +327,8 @@ void DownloadManager::RestartDownload(
 void DownloadManager::CreateDownloadItem(DownloadCreateInfo* info) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
+  download_stats::RecordHistorySize2(history_downloads_.size());
+
   DownloadItem* download = new DownloadItem(this, *info,
                                             browser_context_->IsOffTheRecord());
   int32 download_id = info->download_id;
@@ -682,6 +685,7 @@ int DownloadManager::RemoveDownloads(const base::Time remove_begin) {
 }
 
 int DownloadManager::RemoveAllDownloads() {
+  download_stats::RecordClearAllSize(history_downloads_.size());
   // The null times make the date range unbounded.
   return RemoveDownloadsBetween(base::Time(), base::Time());
 }
@@ -817,6 +821,8 @@ void DownloadManager::OnPersistentStoreQueryComplete(
   // http://crbug.com/84508 is fixed.
   largest_db_handle_in_history_ = 0;
 
+  download_stats::RecordHistorySize(entries->size());
+
   for (size_t i = 0; i < entries->size(); ++i) {
     DownloadItem* download = new DownloadItem(this, entries->at(i));
     // TODO(rdsmith): Remove after http://crbug.com/85408 resolved.
@@ -1068,3 +1074,7 @@ void DownloadManager::SavePageDownloadFinished(DownloadItem* download) {
           Details<DownloadItem>(download));
   }
 }
+
+void DownloadManager::MarkDownloadOpened(int64 db_handle) {
+  delegate_->MarkDownloadOpened(db_handle);
+}