win: Add and use GET_FUNCTION() and GET_FUNCTION_REQUIRED()

handler/win/crashy_test_program.cc

 // Copyright 2015 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
 #include <windows.h>
 #include <winternl.h>
 
 // ntstatus.h conflicts with windows.h so define this locally.
 #ifndef STATUS_NO_SUCH_FILE
 #define STATUS_NO_SUCH_FILE static_cast<NTSTATUS>(0xC000000F)
 #endif
 
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "client/crashpad_client.h"
 #include "tools/tool_support.h"
 #include "util/win/critical_section_with_debug_info.h"
+#include "util/win/get_function.h"
 
 namespace crashpad {
 namespace {
 
 CRITICAL_SECTION g_test_critical_section;
 
 ULONG RtlNtStatusToDosError(NTSTATUS status) {
-  static decltype(::RtlNtStatusToDosError)* rtl_nt_status_to_dos_error =
-      reinterpret_cast<decltype(::RtlNtStatusToDosError)*>(
-          GetProcAddress(LoadLibrary(L"ntdll.dll"), "RtlNtStatusToDosError"));
-  DCHECK(rtl_nt_status_to_dos_error);
+  static const auto rtl_nt_status_to_dos_error =
+      GET_FUNCTION_REQUIRED(L"ntdll.dll", ::RtlNtStatusToDosError);
   return rtl_nt_status_to_dos_error(status);
 }
 
 void AllocateMemoryOfVariousProtections() {
   SYSTEM_INFO system_info;
   GetSystemInfo(&system_info);
 
   const size_t kPageSize = system_info.dwPageSize;
 
   const uint32_t kPageTypes[] = {
@@ skipping 66 matching lines @@
 
   return 0;
 }
 
 }  // namespace
 }  // namespace crashpad
 
 int wmain(int argc, wchar_t* argv[]) {
   return crashpad::ToolSupport::Wmain(argc, argv, crashpad::CrashyMain);
 }