Add ScopedTaskSuspend and its test

util/posix/scoped_fcntl_flags.cc

+// Copyright 2014 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 "util/posix/scoped_fcntl_flags.h"
+
+#include <fcntl.h>
+
+#include "base/logging.h"
+
+namespace crashpad {
+
+ScopedFcntlFlags::ScopedFcntlFlags(int fd, int set_flags, int clear_flags)
+    : fd_(fd),
+      flags_(fcntl(fd_, F_GETFL, 0)) {
+  PCHECK(flags_ != -1);
+
+  int new_flags = (flags_ & (~clear_flags)) | set_flags;
+  int rv = fcntl(fd_, F_SETFL, new_flags);
+  PCHECK(rv != -1);
+}
+
+ScopedFcntlFlags::~ScopedFcntlFlags() {
+  int rv = fcntl(fd_, F_SETFL, flags_);
+  PCHECK(rv != -1);
+}
+
+}  // namespace crashpad