Prevent site engagement scores from decaying when Chrome isn't in use.

chrome/common/pref_names.cc

 // Copyright (c) 2012 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 "chrome/common/pref_names.h"
 
 #include "base/macros.h"
 #include "build/build_config.h"
 #include "chrome/common/pref_font_webkit_names.h"
 
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 // DEPRECATED: this is replaced by kSessionExitType and exists for backwards
 // compatibility.
 const char kSessionExitedCleanly[] = "profile.exited_cleanly";
 
 // A string pref whose values is one of the values defined by
 // |ProfileImpl::kPrefExitTypeXXX|. Set to |kPrefExitTypeCrashed| on startup and
 // one of |kPrefExitTypeNormal| or |kPrefExitTypeSessionEnded| during
 // shutdown. Used to determine the exit type the last time the profile was open.
 const char kSessionExitType[] = "profile.exit_type";
 
+// The last time that the site engagement service recorded an engagement event
+// for this profile for any URL. Recorded only during shutdown. Used to prevent
+// the service from decaying engagement when a user does not use Chrome at all
+// for an extended period of time.
+const char kSiteEngagementLastUpdateTime[] = "profile.last_engagement_time";
+
 // An integer pref. Holds one of several values:
 // 0: unused, previously indicated to open the homepage on startup
 // 1: restore the last session.
 // 2: this was used to indicate a specific session should be restored. It is
 //    no longer used, but saved to avoid conflict with old preferences.
 // 3: unused, previously indicated the user wants to restore a saved session.
 // 4: restore the URLs defined in kURLsToRestoreOnStartup.
 // 5: open the New Tab Page on startup.
 const char kRestoreOnStartup[] = "session.restore_on_startup";
 
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 #endif
 
 // The base64-encoded representation of the public key to use to validate origin
 // trial token signatures.
 const char kOriginTrialPublicKey[] = "origin_trials.public_key";
 
 // A list of origin trial features to disable by policy.
 const char kOriginTrialDisabledFeatures[] = "origin_trials.disabled_features";
 
 }  // namespace prefs