Add ScopedTaskSuspend and its test

util/mach/scoped_task_suspend.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/mach/scoped_task_suspend.h"
+
+#include "base/logging.h"
+#include "base/mac/mach_logging.h"
+
+namespace crashpad {
+
+ScopedTaskSuspend::ScopedTaskSuspend(task_t task) : task_(task) {
+  DCHECK_NE(task_, mach_task_self());
+
+  kern_return_t kr = task_suspend(task_);
+  if (kr != KERN_SUCCESS) {
+    task_ = TASK_NULL;
+    MACH_LOG(ERROR, kr) << "task_suspend";
+  }
+}
+
+ScopedTaskSuspend::~ScopedTaskSuspend() {
+  if (task_ != TASK_NULL) {
+    kern_return_t kr = task_resume(task_);
+    MACH_LOG_IF(ERROR, kr != KERN_SUCCESS, kr) << "task_resume";
+  }
+}
+
+}  // namespace crashpad