Introduce a basic Blink Scheduler

Source/platform/scheduler/Scheduler.cpp

+/*
+ * Copyright (C) 2014 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1.  Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ * 2.  Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
+ *     its contributors may be used to endorse or promote products derived
+ *     from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "platform/scheduler/Scheduler.h"
+
+#include "platform/Task.h"
+#include "platform/TraceEvent.h"
+#include "public/platform/Platform.h"
+
+namespace WebCore {
+
+namespace {
+
+class MainThreadTaskAdapter : public blink::WebThread::Task {

[eseidel, 2014/07/15 15:59:11]

What is this for?

+public:
+    explicit MainThreadTaskAdapter(const Scheduler::Task& task)
+        : m_task(task)
+    {
+    }
+
+    // WebThread::Task implementation.
+    virtual void run() OVERRIDE
+    {
+        TRACE_EVENT0("blink", "MainThreadTaskAdapter::run");
+        m_task();
+    }
+
+private:
+    Scheduler::Task m_task;
+};
+
+}
+
+Scheduler* Scheduler::s_currentScheduler = nullptr;
+
+void Scheduler::initializeOnMainThread()
+{
+    s_currentScheduler = new Scheduler();
+}
+
+void Scheduler::shutdown()
+{
+    delete s_currentScheduler;
+    s_currentScheduler = nullptr;
+}
+
+Scheduler* Scheduler::current()

[eseidel, 2014/07/15 15:59:11]

I believe this method is normally called 'shared' in the codebase.

[Sami, 2014/07/15 19:20:05]

Done.

+{
+    return s_currentScheduler;
+}
+
+Scheduler::Scheduler()
+    : m_mainThread(blink::Platform::current()->currentThread())
+    , m_sharedTimerFunction(nullptr)
+{
+}
+
+Scheduler::~Scheduler()
+{
+}
+
+void Scheduler::scheduleTask(const Task& task)
+{
+    m_mainThread->postTask(new MainThreadTaskAdapter(task));

[eseidel, 2014/07/15 15:59:11]

I see, you want to speak to the Scheduler in terms of SchedulerTasks so you have
something to wrap the SchedulerTasks as Chromium tasks for the chormium message
loop.

[Sami, 2014/07/15 19:20:05]

Right. It's a bit unfortunate we can't share the same closures across that
interface -- perhaps something to revisit later.

+}
+
+void Scheduler::postTask(const Task& task)
+{
+    scheduleTask(task);
+}
+
+void Scheduler::postInputTask(const Task& task)
+{
+    scheduleTask(task);
+}
+
+void Scheduler::postCompositorTask(const Task& task)
+{
+    scheduleTask(task);
+}
+
+void Scheduler::tickSharedTimer()
+{
+    TRACE_EVENT0("blink", "Scheduler::tickSharedTimer");
+    m_sharedTimerFunction();
+}
+
+void Scheduler::sharedTimerAdapter()
+{
+    current()->tickSharedTimer();
+}
+
+void Scheduler::setSharedTimerFiredFunction(void (*function)())
+{
+    m_sharedTimerFunction = function;
+    blink::Platform::current()->setSharedTimerFiredFunction(function ? &Scheduler::sharedTimerAdapter : nullptr);
+}
+
+void Scheduler::setSharedTimerFireInterval(double interval)
+{
+    blink::Platform::current()->setSharedTimerFireInterval(interval);
+}
+
+void Scheduler::stopSharedTimer()
+{
+    blink::Platform::current()->stopSharedTimer();
+}
+
+bool Scheduler::shouldYieldForHighPriorityWork()
+{
+    return false;
+}
+
+} // namespace WebCore