Patch 2/3 to get WebScheduler via WebThread

Source/platform/scheduler/Scheduler.h

-// 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.
-
-#ifndef Scheduler_h
-#define Scheduler_h
-
-#include "platform/PlatformExport.h"
-#include "public/platform/WebThread.h"
-#include "wtf/Functional.h"
-#include "wtf/Noncopyable.h"
-#include "wtf/PassOwnPtr.h"
-
-namespace blink {
-class WebScheduler;
-
-// The scheduler is an opinionated gateway for arranging work to be run on the
-// main thread. It decides which tasks get priority over others based on a
-// scheduling policy and the overall system state.
-class PLATFORM_EXPORT Scheduler {
-    WTF_MAKE_NONCOPYABLE(Scheduler);
-public:
-    // An IdleTask is passed a deadline in CLOCK_MONOTONIC seconds and is expected to complete before this deadline.
-    typedef Function<void(double deadlineSeconds)> IdleTask;
-
-    static Scheduler* shared();
-    static void setForTesting(Scheduler*);
-    static void shutdown();
-
-    // For non-critical tasks which may be reordered relative to other task types and may be starved
-    // for an arbitrarily long time if no idle time is available.
-    void postIdleTask(const WebTraceLocation&, PassOwnPtr<IdleTask>);
-
-    // Like postIdleTask but guarantees that the posted task will not run
-    // nested within an already-running task. Posting an idle task as
-    // non-nestable may not affect when the task gets run, or it could
-    // make it run later than it normally would, but it won't make it
-    // run earlier than it normally would.
-    void postNonNestableIdleTask(const WebTraceLocation&, PassOwnPtr<IdleTask>);
-
-    // Like postIdleTask but does not run the idle task until after some other
-    // task has run. This enables posting of a task which won't stop the Blink
-    // main thread from sleeping, but will start running after it wakes up.
-    void postIdleTaskAfterWakeup(const WebTraceLocation&, PassOwnPtr<IdleTask>);
-
-    // For tasks related to loading, e.g. HTML parsing.  Loading tasks usually have default priority
-    // but they may be deprioritized when the user is interacting with the device.
-    // Takes ownership of |WebThread::Task|.
-    void postLoadingTask(const WebTraceLocation&, WebThread::Task*);
-
-    // Returns true if there is high priority work pending on the main thread
-    // and the caller should yield to let the scheduler service that work.
-    // Must be called on the main thread.
-    bool shouldYieldForHighPriorityWork() const;
-
-    // Returns true if a currently running idle task could exceed its deadline
-    // without impacting user experience too much. This should only be used if
-    // there is a task which cannot be pre-empted and is likely to take longer
-    // than the largest expected idle task deadline. It should NOT be polled to
-    // check whether more work can be performed on the current idle task after
-    // its deadline has expired - post a new idle task for the continuation of
-    // the work in this case.
-    // Must be called from the main thread.
-    bool canExceedIdleDeadlineIfRequired() const;
-
-protected:
-    Scheduler(WebScheduler*);
-    virtual ~Scheduler();
-
-    static Scheduler* s_sharedScheduler;
-    WebScheduler* m_webScheduler;
-};
-
-} // namespace blink
-
-#endif // Scheduler_h