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..d086a5b6daaf699ed87b6657b7affebcb8288fe8 100644
--- a/chrome/browser/ui/cocoa/download/background_theme.mm
+++ b/chrome/browser/ui/cocoa/download/background_theme.mm
@@ -5,6 +5,7 @@
 #include "chrome/browser/ui/cocoa/download/background_theme.h"
 
 #import "chrome/browser/themes/theme_properties.h"
+#include "ui/gfx/color_utils.h"
 
 BackgroundTheme::BackgroundTheme(const ui::ThemeProvider* provider)
     : provider_(provider) {
@@ -47,6 +48,10 @@ 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;
 }