Improve GN header checker, make //ui pass.

ui/compositor/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.
 
 import("//build/config/ui.gni")
 
 component("compositor") {
   sources = [
     "closure_animation_observer.cc",
     "closure_animation_observer.h",
@@ skipping 85 matching lines @@
     "test/test_layer_animation_observer.cc",
     "test/test_layer_animation_observer.h",
     "test/test_layers.cc",
     "test/test_layers.h",
     "test/test_suite.cc",
     "test/test_suite.h",
     "test/test_utils.cc",
     "test/test_utils.h",
   ]
 
+  public_deps = [
+    ":compositor",
+  ]
   deps = [
-    ":compositor",
-    "//base",
+    "//base/test:test_support",
     "//cc",
     "//cc:test_support",
     "//skia",
     "//testing/gtest",
     "//third_party/WebKit/public:blink_minimal",
     "//ui/base",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/gl",
     "//webkit/common/gpu",
@@ skipping 37 matching lines @@
 #    "//ui/gfx",
 #    "//ui/gfx/geometry",
 #    "//ui/gl",
 #    "//ui/resources",
 #  ]
 #
 #  if (is_linux) {
 #    deps += [ "//third_party/mesa:osmesa" ]
 #  }
 #}