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

chrome/browser/ui/views/download/download_shelf_view.cc

Index: chrome/browser/ui/views/download/download_shelf_view.cc
diff --git a/chrome/browser/ui/views/download/download_shelf_view.cc b/chrome/browser/ui/views/download/download_shelf_view.cc
index f60424a4e1b14b7c3968ceeffb6c5f5a96cf0c69..cb4395b020ae5157ef02d08d61b6920d4e9576ca 100644
--- a/chrome/browser/ui/views/download/download_shelf_view.cc
+++ b/chrome/browser/ui/views/download/download_shelf_view.cc
@@ -15,6 +15,7 @@
 #include "chrome/browser/ui/views/download/download_item_view.h"
 #include "chrome/browser/ui/views/frame/browser_view.h"
 #include "content/browser/download/download_item.h"
+#include "content/browser/download/download_stats.h"
 #include "content/browser/download/download_manager.h"
 #include "content/browser/tab_contents/navigation_entry.h"
 #include "grit/generated_resources.h"
@@ -383,6 +384,18 @@ void DownloadShelfView::Show() {
 }
 
 void DownloadShelfView::Close() {
+  download_stats::RecordShelfSize(download_views_.size());
+  int num_pending = 0;
+  size_t i = 0;
+  while (i < download_views_.size()) {
+    DownloadItem* download = download_views_[i]->download();
+    bool is_transfer_done = download->IsComplete() ||
+                            download->IsCancelled() ||
+                            download->IsInterrupted();
+    if (!is_transfer_done)
+      ++num_pending;
+  }
+  download_stats::RecordShelfPendingSize(num_pending);
   parent_->SetDownloadShelfVisible(false);
   shelf_animation_->Hide();
 }