Change chrome:// favicons in tabstrip based on theming.

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

Index: chrome/browser/ui/cocoa/download/background_theme.mm
diff --git a/chrome/browser/ui/cocoa/download/background_theme.mm b/chrome/browser/ui/cocoa/download/background_theme.mm
index b1b8e728c1efb256c44e86579c29fb8acd4ba7c0..a123697ed05a3c95284292f5e055e79a2c34630b 100644
--- a/chrome/browser/ui/cocoa/download/background_theme.mm
+++ b/chrome/browser/ui/cocoa/download/background_theme.mm
@@ -47,6 +47,10 @@ SkColor BackgroundTheme::GetColor(int id) const {
   return SkColor();
 }
 
+color_utils::HSL BackgroundTheme::GetTint(int id) const {
+  return color_utils::HSL();
+}
+
 int BackgroundTheme::GetDisplayProperty(int id) const {
   return -1;
 }