Ozone: Avoid blocking in Swapbuffer Call.

ui/ozone/platform/dri/page_flip_event_handler.cc

+// Copyright 2014 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/ozone/platform/dri/page_flip_event_handler.h"
+
+#include "base/bind.h"
+#include "ui/ozone/platform/dri/hardware_display_controller.h"
+
+namespace ui {
+
+PageFilpEventHandler::PageFilpEventHandler()
+    : base::Thread("PageFilpEventHandler"),
+      child_message_loop_proxy_(base::MessageLoopProxy::current()),
+      polling_(true, true) {

[brianderson, 2014/12/10 22:48:05]

This should probably be polling_(true, false).

+  base::Thread::Options options;
+  options.message_loop_type = base::MessageLoop::TYPE_IO;
+  StartWithOptions(options);
+  SetPriority(base::kThreadPriority_Background);
+}
+
+PageFilpEventHandler::~PageFilpEventHandler() {
+}
+
+void PageFilpEventHandler::EnsurePreviousFlipHandled() {
+  polling_.Wait();
+}
+
+void PageFilpEventHandler::GetPageFlipCompleted(
+    HardwareDisplayController* controller,
+    const ui::SurfaceOzoneEGL::PageFlipCompletionCallback& callback) {
+  message_loop_proxy()->PostTask(
+      FROM_HERE, base::Bind(&PageFilpEventHandler::CheckPageFlipEvent, this,
+                            controller, callback));
+}
+
+void PageFilpEventHandler::CleanUp() {
+  SetThreadWasQuitProperly(true);
+}
+
+void PageFilpEventHandler::RunFlipEventCallBack(
+    const ui::SurfaceOzoneEGL::PageFlipCompletionCallback& callback) {
+  callback.Run();
+}
+
+void PageFilpEventHandler::CheckPageFlipEvent(
+    PageFilpEventHandler* data,
+    HardwareDisplayController* controller,
+    const ui::SurfaceOzoneEGL::PageFlipCompletionCallback& callback) {
+  data->polling_.Reset();

[brianderson, 2014/12/10 22:48:05]

This should be a DCHECK that IsSignaled is false. If it's not, there's likely a
race condition if EnsurePreviousFlipHandled is called before this task gets
scheduled.

+  controller->WaitForPageFlipEvent();
+  data->polling_.Signal();
+  data->child_message_loop_proxy_->PostTask(
+      FROM_HERE,
+      base::Bind(&PageFilpEventHandler::RunFlipEventCallBack, callback));
+}
+
+}  // namespace ui