Mac: Add tooltip to download item.

chrome/browser/cocoa/download_item_controller.mm

Index: chrome/browser/cocoa/download_item_controller.mm
diff --git a/chrome/browser/cocoa/download_item_controller.mm b/chrome/browser/cocoa/download_item_controller.mm
index 02dcd66036c93163a98bbae8905b4c80d50e1f16..ccc27704e2703de89d4dc3a26e42561ec97f924b 100644
--- a/chrome/browser/cocoa/download_item_controller.mm
+++ b/chrome/browser/cocoa/download_item_controller.mm
@@ -36,6 +36,10 @@ const int kTextWidth = 140;            // Pixels
 // dangerous download message.
 const int kFileNameMaxLength = 20;
 
+// The maximum width in pixels for the file name tooltip.
+const int kToolTipMaxWidth = 900;
+
+
 // Helper to widen a view.
 void WidenView(NSView* view, CGFloat widthChange) {
   // If it is an NSBox, the autoresize of the contentView is the issue.
@@ -150,6 +154,7 @@ class DownloadShelfContextMenuMac : public DownloadShelfContextMenu {
   [image_ setImage:alertIcon];
 
   bridge_->LoadIcon();
+  [self updateToolTip];
 }
 
 - (void)setStateFromDownload:(BaseDownloadItemModel*)downloadModel {
@@ -254,6 +259,13 @@ class DownloadShelfContextMenuMac : public DownloadShelfContextMenu {
   return bridge_->download_model()->download();
 }
 
+- (void)updateToolTip {
+  std::wstring elidedFilename = gfx::ElideFilename(
+      [self download]->GetFileName(),
+      gfx::Font(), kToolTipMaxWidth);
+  [progressView_ setToolTip:base::SysWideToNSString(elidedFilename)];
+}
+
 - (void)clearDangerousMode {
   [self setState:kNormal];
   // The state change hide the dangerouse download view and is now showing the