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

chrome/browser/cocoa/bookmark_bar_view.mm

Index: chrome/browser/cocoa/bookmark_bar_view.mm
diff --git a/chrome/browser/cocoa/bookmark_bar_view.mm b/chrome/browser/cocoa/bookmark_bar_view.mm
index d62b7555ed53735e2194c001723d0933df79df3a..61cfa679076d02396a7e8df908506bf1038dd760 100644
--- a/chrome/browser/cocoa/bookmark_bar_view.mm
+++ b/chrome/browser/cocoa/bookmark_bar_view.mm
@@ -40,11 +40,14 @@
     [self updateTheme:[self gtm_theme]];
 }
 
+// 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:GTMThemeStyleBookmarksBarButton
                                       state:GTMThemeStateActiveWindow];