Linux: Add multi-threaded message loop support (issue #2512)

tests/cefclient/browser/util_gtk.cc

@@ -0,0 +1,33 @@
+// Copyright (c) 2018 The Chromium Embedded Framework 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 "tests/cefclient/browser/util_gtk.h"
+
+#include <gdk/gdk.h>
+
+namespace client {
+
+base::PlatformThreadId ScopedGdkThreadsEnter::locked_thread_ =
+    kInvalidPlatformThreadId;
+
+ScopedGdkThreadsEnter::ScopedGdkThreadsEnter() {
+  // The GDK lock is not reentrant, so don't try to lock again if the current
+  // thread already holds it.
+  base::PlatformThreadId current_thread = base::PlatformThread::CurrentId();
+  take_lock_ = current_thread != locked_thread_;
+
+  if (take_lock_) {
+    gdk_threads_enter();
+    locked_thread_ = current_thread;
+  }
+}
+
+ScopedGdkThreadsEnter::~ScopedGdkThreadsEnter() {
+  if (take_lock_) {
+    locked_thread_ = kInvalidPlatformThreadId;
+    gdk_threads_leave();
+  }
+}
+
+}  // namespace client