base: add a thread-safety assertion checker

base/thread_restrictions.cc

Index: base/thread_restrictions.cc
diff --git a/base/thread_restrictions.cc b/base/thread_restrictions.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5be8ad7133d390341fc1573c54efd64a2b591724
--- /dev/null
+++ b/base/thread_restrictions.cc
@@ -0,0 +1,42 @@
+// Copyright (c) 2010 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 "base/thread_restrictions.h"
+
+// This entire file is compiled out in Release mode.
+#ifndef NDEBUG
+
+#include "base/lazy_instance.h"
+#include "base/logging.h"
+#include "base/thread_local.h"
+
+namespace {
+
+static base::LazyInstance<base::ThreadLocalBoolean>
+    g_io_disallowed(base::LINKER_INITIALIZED);
+
+}  // anonymous namespace
+
+namespace base {
+
+// static
+void ThreadRestrictions::SetIOAllowed(bool allowed) {
+  g_io_disallowed.Get().Set(!allowed);
+}
+
+// static
+void ThreadRestrictions::AssertIOAllowed() {
+  if (g_io_disallowed.Get().Get()) {
+    LOG(FATAL) <<
+        "Function marked as IO-only was called from a thread that "
+        "disallows IO!  If this thread really should be allowed to "
+        "make IO calls, adjust the call to "
+        "base::ThreadRestrictions::SetIOAllowed() in this thread's "
+        "startup.";
+  }
+}
+
+}  // namespace base
+
+#endif  // NDEBUG