Clean up GTK3 build flags.

build/config/linux/gtk3/BUILD.gn

Index: build/config/linux/gtk3/BUILD.gn
diff --git a/build/config/linux/gtk3/BUILD.gn b/build/config/linux/gtk3/BUILD.gn
index 69974c1e6c5da266e4d1ac1895916cf0e5b2b198..0cfd05f319345c81508aa0bed572ecb545e972a1 100644
--- a/build/config/linux/gtk3/BUILD.gn
+++ b/build/config/linux/gtk3/BUILD.gn
@@ -6,7 +6,8 @@ import("//build/config/linux/pkg_config.gni")
 
 assert(is_linux, "This file should only be referenced on Linux")
 
-# Depend on //build/config/linux/gtk3 to use GTKv3.
+# Depend on //build/config/linux/gtk3 to use GTKv3. Depend on
+# //build/config/linux/gtk to get GTK 2 or 3 depending on the build flags.
 #
 # GN doesn't check visibility for configs so we give this an obviously internal
 # name to discourage random targets from accidentally depending on this and
@@ -22,21 +23,16 @@ pkg_config("gtk3_internal_config") {
 }
 
 # Basically no parts of Chrome should depend on GTK. To prevent accidents, the
-# parts that explicitly need GTK are whitelisted on this target.
+# parts that explicitly need GTK3 are whitelisted on this target.
 group("gtk3") {
   visibility = [
-    "//chrome/browser/ui/libgtkui:libgtk3ui",
-    "//gpu/gles2_conform_support:gles2_conform_test_windowless",
-    "//remoting/host",
-    "//remoting/host/it2me:common",
-    "//remoting/host/it2me:remote_assistance_host",
-    "//remoting/host:remoting_me2me_host_static",
-    "//remoting/test:it2me_standalone_host_main",
+    "//build/config/linux/gtk",
+    "//chrome/browser/ui/libgtkui:*",
   ]
   public_configs = [ ":gtk3_internal_config" ]
 }
 
-# Depend on "gtkprint" to get this.
+# Depend on "gtkprint3" to get this.
 pkg_config("gtkprint3_internal_config") {
   packages = [ "gtk+-unix-print-3.0" ]
 }