linux: Both gtk and the aura port should set the icon theme name.

chrome/browser/ui/gtk/gtk_theme_service.cc

Index: chrome/browser/ui/gtk/gtk_theme_service.cc
diff --git a/chrome/browser/ui/gtk/gtk_theme_service.cc b/chrome/browser/ui/gtk/gtk_theme_service.cc
index 2ffcee5c1028f4e731176d1385994916e9a06524..086693d81a5f7bcf1d2238a8af76cdae9cec7ea4 100644
--- a/chrome/browser/ui/gtk/gtk_theme_service.cc
+++ b/chrome/browser/ui/gtk/gtk_theme_service.cc
@@ -11,6 +11,7 @@
 
 #include "base/debug/trace_event.h"
 #include "base/environment.h"
+#include "base/nix/mime_util_xdg.h"
 #include "base/nix/xdg_util.h"
 #include "base/prefs/pref_service.h"
 #include "base/stl_util.h"
@@ -628,6 +629,7 @@ void GtkThemeService::LoadThemePrefs() {
     ThemeService::LoadThemePrefs();
   }
 
+  SetXDGIconTheme();
   RebuildMenuIconSets();
 }
 
@@ -676,12 +678,22 @@ void GtkThemeService::OnStyleSet(GtkWidget* widget,
   if (profile()->GetPrefs()->GetBoolean(prefs::kUsesSystemTheme)) {
     ClearAllThemeData();
     LoadGtkValues();
+    SetXDGIconTheme();
     NotifyThemeChanged();
   }
 
   RebuildMenuIconSets();
 }
 
+void GtkThemeService::SetXDGIconTheme() {
+  gchar* gtk_theme_name;
+  g_object_get(gtk_settings_get_default(),
+               "gtk-icon-theme-name",
+               &gtk_theme_name, NULL);
+  base::nix::SetIconThemeName(gtk_theme_name);
+  g_free(gtk_theme_name);
+}
+
 void GtkThemeService::LoadGtkValues() {
   // Before we start setting images and values, we have to clear out old, stale
   // values. (If we don't do this, we'll regress startup time in the case where