Update Windows It2Me to allow remote users to interact with elevated windows

remoting/host/win/launch_native_messaging_host_process.cc

 // 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.
 
 #include "remoting/host/win/launch_native_messaging_host_process.h"
 
 #include <windows.h>
 #include <shellapi.h>
 
 #include <cstdint>
 #include <string>
 
 #include "base/command_line.h"
 #include "base/files/file_path.h"
+#include "base/files/file_util.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/win/win_util.h"
 #include "ipc/ipc_channel.h"
 #include "remoting/host/switches.h"
 #include "remoting/host/win/security_descriptor.h"
 
 namespace {
@@ skipping 35 matching lines @@
 
 ProcessLaunchResult LaunchNativeMessagingHostProcess(
     const base::FilePath& binary_path,
     intptr_t parent_window_handle,
     bool elevate_process,
     base::win::ScopedHandle* read_handle,
     base::win::ScopedHandle* write_handle) {
   DCHECK(read_handle);
   DCHECK(write_handle);
 
+  if (!base::PathExists(binary_path)) {
+    LOG(ERROR) << "Cannot find binary: " << binary_path.value();
+    return PROCESS_LAUNCH_RESULT_FAILED;
+  }
+
   // presubmit: allow wstring
   std::wstring user_sid;
   if (!base::win::GetUserSidString(&user_sid)) {
     LOG(ERROR) << "Failed to query the current user SID.";
     return PROCESS_LAUNCH_RESULT_FAILED;
   }
 
   // Create a security descriptor that gives full access to the caller and
   // BUILTIN_ADMINISTRATORS and denies access by anyone else.
   // Local admins need access because the privileged host process will run
@@ skipping 89 matching lines @@
       return PROCESS_LAUNCH_RESULT_FAILED;
     }
   }
 
   read_handle->Set(temp_read_handle.Take());
   write_handle->Set(temp_write_handle.Take());
   return PROCESS_LAUNCH_RESULT_SUCCESS;
 }
 
 }  // namespace remoting