Address post-commit comments from codereview.chromium.org/371059 and codereview.chromium.org/293019

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 3bd09057d383aa648f7cead7d814d7bc9d5f6aa4..a17b202d667b6411868dd24ec3b41e8da511a95b 100644
--- a/chrome/browser/cocoa/download_item_controller.mm
+++ b/chrome/browser/cocoa/download_item_controller.mm
@@ -238,11 +238,14 @@ class DownloadShelfContextMenuMac : public DownloadShelfContextMenu {
   [shelf_ layoutItems];
 }
 
+// Called after the current theme has changed.
 - (void)themeDidChangeNotification:(NSNotification*)aNotification {
   GTMTheme* theme = [aNotification object];
   [self updateTheme:theme];
 }
 
+// Adapt appearance to the current theme. Called after theme changes and before
+// this is shown for the first time.
 - (void)updateTheme:(GTMTheme*)theme {
   NSColor* color = [theme textColorForStyle:GTMThemeStyleTabBarSelected
                                       state:GTMThemeStateActiveWindow];