
Follow up to https://chromium-review.googlesource.com/c/chromium/src/+/2196817 Bug: 1079458 Change-Id: I22dc45f0399b3978e494ab20b66ef5126ccea580 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2231906 Auto-Submit: Ben Goldberger <benwgold@google.com> Reviewed-by: Theresa <twellington@chromium.org> Reviewed-by: Yaron Friedman <yfriedman@chromium.org> Reviewed-by: Alexei Svitkine <asvitkine@chromium.org> Commit-Queue: Yaron Friedman <yfriedman@chromium.org> Cr-Commit-Position: refs/heads/master@{#790414}
77 lines
3.2 KiB
C++
77 lines
3.2 KiB
C++
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef CONTENT_BROWSER_FIELD_TRIAL_SYNCHRONIZER_H_
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#define CONTENT_BROWSER_FIELD_TRIAL_SYNCHRONIZER_H_
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#include <string>
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#include <vector>
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#include "base/macros.h"
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#include "base/memory/ref_counted.h"
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#include "base/metrics/field_trial.h"
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#include "components/variations/variations_ids_provider.h"
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namespace content {
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class RenderProcessHost;
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// This class is used by the browser process to communicate FieldTrial setting
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// (field trial name and group) and Variation header to any previously started
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// renderers.
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//
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// This class registers itself as an observer of FieldTrialList. FieldTrialList
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// notifies this class by calling it's OnFieldTrialGroupFinalized method when a
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// group is selected (finalized) for a FieldTrial and OnFieldTrialGroupFinalized
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// method sends the FieldTrial's name and the group to all renderer processes.
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// Each renderer process creates the FieldTrial, and by using a 100% probability
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// for the FieldTrial, forces the FieldTrial to have the same group string.
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// This class also registers itself as a VariationsIdsProvider Observer
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// and updates the renderers if the variations header changes.
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class FieldTrialSynchronizer
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: public base::RefCountedThreadSafe<FieldTrialSynchronizer>,
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public base::FieldTrialList::Observer,
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public variations::VariationsIdsProvider::Observer {
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public:
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// Construction also sets up the global singleton instance. This instance is
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// used to communicate between the UI and other threads, and is destroyed only
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// as the main thread (browser_main) terminates, which means all other threads
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// have completed, and will not need this instance any further. It adds itself
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// as an observer of FieldTrialList so that it gets notified whenever a group
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// is finalized in the browser process.
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FieldTrialSynchronizer();
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// FieldTrialList::Observer methods:
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// This method is called by the FieldTrialList singleton when a trial's group
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// is finalized. This method contacts all renderers (by calling
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// NotifyAllRenderers) to create a FieldTrial that carries the randomly
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// selected state from the browser process into all the renderer processes.
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void OnFieldTrialGroupFinalized(const std::string& name,
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const std::string& group_name) override;
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// VariationsIdsProvider::Observer methods:
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void VariationIdsHeaderUpdated() override;
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// Sends the current variations header to |host|'s renderer.
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static void UpdateRendererVariationsHeader(RenderProcessHost* host);
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private:
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// Notify all renderer processes about the |group_name| that is finalized for
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// the given field trail (|field_trial_name|). This is called on UI thread.
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void NotifyAllRenderersOfFieldTrial(const std::string& field_trial_name,
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const std::string& group_name);
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static void NotifyAllRenderersOfVariationsHeader();
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friend class base::RefCountedThreadSafe<FieldTrialSynchronizer>;
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~FieldTrialSynchronizer() override;
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DISALLOW_COPY_AND_ASSIGN(FieldTrialSynchronizer);
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};
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} // namespace content
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#endif // CONTENT_BROWSER_FIELD_TRIAL_SYNCHRONIZER_H_
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