Bug 1134518 - Cap shistory entries in the SessionWorker when shutting down r=Yoric

browser/components/sessionstore/SessionFile.jsm

@@ -55,6 +55,9 @@ XPCOMUtils.defineLazyModuleGetter(this, "SessionWorker",
 const PREF_UPGRADE_BACKUP = "browser.sessionstore.upgradeBackup.latestBuildID";
 const PREF_MAX_UPGRADE_BACKUPS = "browser.sessionstore.upgradeBackup.maxUpgradeBackups";
 
+const PREF_MAX_SERIALIZE_BACK = "browser.sessionstore.max_serialize_back";
+const PREF_MAX_SERIALIZE_FWD = "browser.sessionstore.max_serialize_forward";
+
 this.SessionFile = {
   /**
    * Read the contents of the session file, asynchronously.
@@ -256,11 +259,11 @@ let SessionFileInternal = {
 
     // Initialize the worker to let it handle backups and also
     // as a workaround for bug 964531.
-    SessionWorker.post("init", [
-      result.origin,
-      this.Paths,
-      Preferences.get(PREF_MAX_UPGRADE_BACKUPS, 3)
-    ]);
+    SessionWorker.post("init", [result.origin, this.Paths, {
+      maxUpgradeBackups: Preferences.get(PREF_MAX_UPGRADE_BACKUPS, 3),
+      maxSerializeBack: Preferences.get(PREF_MAX_SERIALIZE_BACK, 10),
+      maxSerializeForward: Preferences.get(PREF_MAX_SERIALIZE_FWD, -1)
+    }]);
 
     return result;
   }),

browser/components/sessionstore/SessionWorker.js

@@ -88,15 +88,25 @@ let Agent = {
    * @param {string} origin Which of sessionstore.js or its backups
    *   was used. One of the `STATE_*` constants defined above.
    * @param {object} paths The paths at which to find the various files.
-   * @param {number} maxUpgradeBackups The number of old upgrade backups that should be kept.
+   * @param {object} prefs The preferences the worker needs to known.
    */
-  init: function (origin, paths, maxUpgradeBackups) {
+  init(origin, paths, prefs = {}) {
     if (!(origin in paths || origin == STATE_EMPTY)) {
       throw new TypeError("Invalid origin: " + origin);
     }
+
+    // Check that all required preference values were passed.
+    for (let pref of ["maxUpgradeBackups", "maxSerializeBack", "maxSerializeForward"]) {
+      if (!prefs.hasOwnProperty(pref)) {
+        throw new TypeError(`Missing preference value for ${pref}`);
+      }
+    }
+
     this.state = origin;
     this.Paths = paths;
-    this.maxUpgradeBackups = maxUpgradeBackups || 3;
+    this.maxUpgradeBackups = prefs.maxUpgradeBackups;
+    this.maxSerializeBack = prefs.maxSerializeBack;
+    this.maxSerializeForward = prefs.maxSerializeForward;
     this.upgradeBackupNeeded = paths.nextUpgradeBackup != paths.upgradeBackup;
     return {result: true};
   },
@@ -118,6 +128,26 @@ let Agent = {
     let exn;
     let telemetry = {};
 
+    // Cap the number of backward and forward shistory entries on shutdown.
+    if (options.isFinalWrite) {
+      for (let window of state.windows) {
+        for (let tab of window.tabs) {
+          let lower = 0;
+          let upper = tab.entries.length;
+
+          if (this.maxSerializeBack > -1) {
+            lower = Math.max(lower, tab.index - this.maxSerializeBack - 1);
+          }
+          if (this.maxSerializeForward > -1) {
+            upper = Math.min(upper, tab.index + this.maxSerializeForward);
+          }
+
+          tab.entries = tab.entries.slice(lower, upper);
+          tab.index -= lower;
+        }
+      }
+    }
+
     let stateString = JSON.stringify(state);
     let data = Encoder.encode(stateString);
     let startWriteMs, stopWriteMs;