Make gtk2/gtk3 compile time switchable.

gpu/gles2_conform_support/BUILD.gn

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 declare_args() {
   # Set to true to compile with the OpenGL ES 2.0 conformance tests.
   internal_gles2_conform_tests = false
 }
 
 import("//build/config/allocator.gni")
@@ skipping 62 matching lines @@
     ]
     deps = [
       ":generate_gles2_conform_embedded_data",
       "//gpu/gles2_conform_support/egl",
       "//gpu/gles2_conform_support/native:windowless",
       "//gpu/command_buffer/client:gles2_c_libnocheck",
     ]
     configs += [ "//build/compiler:no_incompatible_pointer_warnings" ]
     if (is_linux) {
       if (!is_chromeos) {
-        deps += [ "//build/linux/system/gtk" ]
+        deps += [ "//build/linux/system/gtk2" ]
 
         if (is_clang) {
           cflags = [
             "-Wno-array-bounds",
             "-Wno-implicit-function-declaration",
             "-Wno-parentheses-equality",
             "-Wno-pointer-sign",
             "-Wno-return-type",
             "-Wno-sizeof-pointer-memaccess",
             "-Wno-tautological-compare",
@@ skipping 86 matching lines @@
   data = [
     "gles2_conform_test_expectations.txt",
   ]
 
   if (internal_gles2_conform_tests) {
     deps += [ "gles2_conform_test_windowless" ]
 
     data_deps = [ "//third_party/gles2_conform/GTF_ES/" ]
   }
 }