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

ui/views_content_client/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("views_content_client") {
   testonly = true
   sources = [
     "views_content_browser_client.cc",
     "views_content_browser_client.h",
     "views_content_client.cc",
     "views_content_client.h",
     "views_content_client_export.h",
     "views_content_client_main_parts.cc",
     "views_content_client_main_parts.h",
     "views_content_client_main_parts_chromeos.cc",
     "views_content_client_main_parts_mac.mm",
     "views_content_main_delegate.cc",
+    "views_content_main_delegate.h",
   ]
 
   defines = [ "VIEWS_CONTENT_CLIENT_IMPLEMENTATION" ]
 
   deps = [
     "//base",
     "//base:i18n",
     "//content",
     "//content/shell:content_shell_lib",
     "//third_party/icu",
@@ skipping 25 matching lines @@
     ]
   }
 
   if (is_chromeos) {
     deps += [
       "//ui/aura:test_support",
       "//ui/wm:test_support",
     ]
   }
 }