Show download interrupt reason in a tooltip

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

Index: chrome/browser/ui/cocoa/download/download_item_controller.mm
diff --git a/chrome/browser/ui/cocoa/download/download_item_controller.mm b/chrome/browser/ui/cocoa/download/download_item_controller.mm
index faac76d7ef690268f108ad453d8df683d24d9334..a406a8d0be279b231e2288dd9dae71c47720dc51 100644
--- a/chrome/browser/ui/cocoa/download/download_item_controller.mm
+++ b/chrome/browser/ui/cocoa/download/download_item_controller.mm
@@ -245,9 +245,19 @@ class DownloadShelfContextMenuMac : public DownloadShelfContextMenu {
 }
 
 - (void)updateToolTip {
-  string16 elidedFilename = ui::ElideFilename(
+  string16 tooltip_text = ui::ElideFilename(
       [self download]->GetFileNameToReportUser(), *font_, kToolTipMaxWidth);
-  [progressView_ setToolTip:base::SysUTF16ToNSString(elidedFilename)];
+
+  if ([self download]->GetState() == content::DownloadItem::INTERRUPTED) {
+    content::DownloadInterruptReason reason = [self download]->GetLastReason();
+    DCHECK_NE(0, reason);
+
+    // Add the status on another line.
+    tooltip_text += ASCIIToUTF16("\n");
+    tooltip_text += DownloadItemModel::InterruptReasonStatusMessage(reason);
+  }
+
+  [progressView_ setToolTip:base::SysUTF16ToNSString(tooltip_text)];
 }
 
 - (void)clearDangerousMode {