third_party/WebKit/public/platform/WebViewScheduler.h

// Copyright 2015 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 WebViewScheduler_h
#define WebViewScheduler_h

#include "WebCommon.h"
#include "public/platform/BlameContext.h"

#include <memory>

namespace blink {

class WebFrameScheduler;

class BLINK_PLATFORM_EXPORT WebViewScheduler {
public:
    virtual ~WebViewScheduler() { }

    // The scheduler may throttle tasks associated with background pages.
    virtual void setPageVisible(bool) = 0;

    // Creates a new WebFrameScheduler. The caller is responsible for deleting
    // it. All tasks executed by the frame scheduler will be attributed to
    // |BlameContext|.
    virtual std::unique_ptr<WebFrameScheduler> createFrameScheduler(BlameContext*) = 0;

    // Instructs this WebViewScheduler to use virtual time. When virtual time is enabled
    // the system doesn't actually sleep for the delays between tasks before executing
    // them. E.g: A-E are delayed tasks
    //
    // |    A   B C  D           E  (normal)
    // |-----------------------------> time
    //
    // |ABCDE                       (virtual time)
    // |-----------------------------> time
    virtual void enableVirtualTime() = 0;

    // Returns true if virtual time is currently allowed to advance.
    virtual bool virtualTimeAllowedToAdvance() const = 0;

    enum class VirtualTimePolicy {
        // In this policy virtual time is allowed to advance. If the blink scheduler runs out of
        // immediate work, the virtual timebase will be incremented so that the next sceduled
        // timer may fire.  NOTE Tasks will be run in time order (as usual).
        ADVANCE,

        // In this policy virtual time is not allowed to advance. Delayed tasks posted to
        // WebTaskRunners owned by any child WebFrameSchedulers will be paused, unless their
        // scheduled run time is less than or equal to the current virtual time.  Note non-delayed
        // tasks will run as normal.
        PAUSE,

        // In this policy virtual time is allowed to advance unless there are pending network
        // fetches associated any child WebFrameScheduler.
        PAUSE_IF_NETWORK_FETCHES_PENDING
    };

    // Sets the virtual time policy, which is applied imemdiatly to all child WebFrameSchedulers.
    virtual void setVirtualTimePolicy(VirtualTimePolicy) = 0;
};

} // namespace blink

#endif // WebViewScheduler