Clean up GTK3 build flags.

chrome/browser/ui/BUILD.gn

Index: chrome/browser/ui/BUILD.gn
diff --git a/chrome/browser/ui/BUILD.gn b/chrome/browser/ui/BUILD.gn
index 06b013e6fd4d8e721e597104820dd7a16b301402..4676febd2b5bd8f1c014eccf2c04a93a214b657e 100644
--- a/chrome/browser/ui/BUILD.gn
+++ b/chrome/browser/ui/BUILD.gn
@@ -1926,12 +1926,8 @@ split_static_library("ui") {
     deps += [ "//build/linux/libgio" ]
   }
   if (use_aura && !use_ozone && is_desktop_linux) {
-    # These are the only components that can interact with gtk.
-    if (use_gtk3) {
-      deps += [ "//chrome/browser/ui/libgtkui:libgtk3ui" ]
-    } else {
-      deps += [ "//chrome/browser/ui/libgtkui:libgtk2ui" ]
-    }
+    # This is the only component that can interact with gtk.
+    deps += [ "//chrome/browser/ui/libgtkui" ]
   }
   if (is_win || is_mac || is_desktop_linux) {
     sources += [