ui/compositor: use an IO message loop on posix instead of DEFAULT

ui/compositor/compositor.cc

 // Copyright (c) 2012 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 "ui/compositor/compositor.h"
 
 #include <algorithm>
 #include <deque>
 
 #include "base/bind.h"
@@ skipping 473 matching lines @@
       switches::kUIDisableThreadedCompositing);
 #else
   bool use_thread =
       CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kUIEnableThreadedCompositing) &&
       !CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kUIDisableThreadedCompositing);
 #endif
   if (use_thread) {
     g_compositor_thread = new base::Thread("Browser Compositor");
+#if defined(OS_POSIX)
+    // Workaround for crbug.com/293736
+    // On Posix, MessagePumpDefault uses system time, so delayed tasks (for
+    // compositor scheduling) work incorrectly across system time changes (e.g.
+    // tlsdate). So instead, use an IO loop, which uses libevent, that uses
+    // monotonic time (immune to these problems).
+    base::Thread::Options options;
+    options.message_loop_type = base::MessageLoop::TYPE_IO;
+    g_compositor_thread->StartWithOptions(options);
+#else
     g_compositor_thread->Start();
+#endif
   }
 
   DCHECK(!g_compositor_initialized) << "Compositor initialized twice.";
   g_compositor_initialized = true;
 }
 
 // static
 bool Compositor::WasInitializedWithThread() {
   return !!g_compositor_thread;
 }
@@ skipping 266 matching lines @@
 }
 
 void Compositor::NotifyEnd() {
   last_ended_frame_++;
   FOR_EACH_OBSERVER(CompositorObserver,
                     observer_list_,
                     OnCompositingEnded(this));
 }
 
 }  // namespace ui