Enable more tests in GN build.

ui/views/controls/webview/BUILD.gn

 # Copyright 2014 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.
 
 component("webview") {
   sources = [
     "unhandled_keyboard_event_handler.cc",
     "unhandled_keyboard_event_handler.h",
     "unhandled_keyboard_event_handler_linux.cc",
     "unhandled_keyboard_event_handler_win.cc",
@@ skipping 18 matching lines @@
     "//ui/gfx/geometry",
     "//ui/web_dialogs",
     "//ui/views",
     "//url",
   ]
 
   forward_dependent_configs_from = [
     "//ui/views",
   ]
 }
+
+source_set("test_support") {
+  sources = [
+    "../../test/webview_test_helper.cc",
+    "../../test/webview_test_helper.h",
+  ]
+
+  deps = [
+    ":webview",
+    "//base",
+    "//content",
+    "//ipc",
+    "//skia",
+    "//testing/gtest",
+    "//ui/aura",
+    "//ui/base",
+    "//ui/events",
+    "//ui/gfx",
+    "//ui/gfx/geometry",
+    "//ui/views",
+    "//ui/views:test_support",
+    #'../../../../content/content_shell_and_tests.gyp:test_support_content',  TODO(GYP)
+  ]
+}