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

chrome/browser/ui/cocoa/download/download_shelf_controller.mm

Index: chrome/browser/ui/cocoa/download/download_shelf_controller.mm
diff --git a/chrome/browser/ui/cocoa/download/download_shelf_controller.mm b/chrome/browser/ui/cocoa/download/download_shelf_controller.mm
index fb69b913340d9eaddedf312fc7cb97566db84aa4..15d88c7febabeff9b042aab356db288b38e5689c 100644
--- a/chrome/browser/ui/cocoa/download/download_shelf_controller.mm
+++ b/chrome/browser/ui/cocoa/download/download_shelf_controller.mm
@@ -20,6 +20,7 @@
 #import "chrome/browser/ui/cocoa/presentation_mode_controller.h"
 #include "content/browser/download/download_item.h"
 #include "content/browser/download/download_manager.h"
+#include "content/browser/download/download_stats.h"
 #import "third_party/GTM/AppKit/GTMNSAnimation+Duration.h"
 #include "ui/base/l10n/l10n_util.h"
 
@@ -240,6 +241,21 @@ const NSSize kHoverCloseButtonDefaultSize = { 16, 16 };
 - (void)hide:(id)sender {
   [self cancelAutoCloseAndRemoveTrackingArea];
 
+  download_stats::RecordShelfSize([downloadItemControllers_ count]);

[Randy Smith (Not in Mondays), 2011/09/30 15:57:21]

I believe that on some platforms, but not others, download shelves will
auto-close when the last unopened download is opened.  How will this affect the
statistics?

(At a minimum you should alter the CL description.  But I'd suggest putting some
thought into what this'll mean for stat interpretation.)

[benjhayden, 2011/10/03 20:54:39]

I went ahead and split the stat.

+
+  int numPending = 0;
+  for (NSUInteger i = 0; i < [downloadItemControllers_ count]; ++i) {
+    DownloadItemController* itemController =
+        [downloadItemControllers_ objectAtIndex:i];
+    DownloadItem* download = [itemController download];
+    bool isTransferDone = download->IsComplete() ||
+                          download->IsCancelled() ||
+                          download->IsInterrupted();

[Randy Smith (Not in Mondays), 2011/09/30 15:57:21]

Is there a reason we're not just counting number in progress?

[benjhayden, 2011/10/03 20:54:39]

Done.

+    if (!isTransferDone)
+      ++numPending;
+  }
+  download_stats::RecordShelfPendingSize(numPending);
+
   // If |sender| isn't nil, then we're being closed from the UI by the user and
   // we need to tell our shelf implementation to close. Otherwise, we're being
   // closed programmatically by our shelf implementation.