Add missing .h files to .gn files that have a .cc file next to it in the gn file already.

ui/ozone/platform/wayland/BUILD.gn

 # Copyright 2016 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.
 
 visibility = [ "//ui/ozone/*" ]
 
 import("//build/config/linux/pkg_config.gni")
 
 pkg_config("wayland-egl") {
   packages = [ "wayland-egl" ]
@@ skipping 57 matching lines @@
   ]
 }
 
 source_set("wayland_unittests") {
   testonly = true
 
   sources = [
     "fake_server.cc",
     "fake_server.h",
     "mock_platform_window_delegate.cc",
+    "mock_platform_window_delegate.h",
     "wayland_connection_unittest.cc",
     "wayland_keyboard_unittest.cc",
     "wayland_pointer_unittest.cc",
     "wayland_surface_factory_unittest.cc",
     "wayland_test.cc",
     "wayland_test.h",
     "wayland_window_unittest.cc",
   ]
 
   deps = [
     ":wayland",
     "//testing/gmock",
     "//testing/gtest",
     "//third_party/wayland:wayland_server",
     "//third_party/wayland-protocols:xdg_shell_protocol",
     "//ui/gfx:test_support",
     "//ui/ozone:platform",
   ]
 
   defines = [ "WL_HIDE_DEPRECATED" ]
 }