Bug 670040: Make nsISessionStartup.state a jsval to save repeatedly stringifying/parsing the initial state. r=zpao

browser/components/sessionstore/nsISessionStartup.idl

@@ -43,11 +43,11 @@
  * - and allows to restore everything into one window.
  */
 
-[scriptable, uuid(e7bb7828-0e32-4995-a848-4aa35df603c7)]
+[scriptable, uuid(170c6857-7f71-46ce-bc9b-185723b1c3a8)]
 interface nsISessionStartup: nsISupports
 {
-  // Get session state as string
+  // Get session state
-  readonly attribute AString state;
+  readonly attribute jsval state;
 
   /**
    * Determine if session should be restored 

browser/components/sessionstore/src/nsSessionStartup.js

@@ -89,7 +89,7 @@ function SessionStartup() {
 SessionStartup.prototype = {
 
   // the state to restore at startup
-  _iniString: null,
+  _initialState: null,
   _sessionType: Ci.nsISessionStartup.NO_SESSION,
 
 /* ........ Global Event Handlers .............. */
@@ -121,31 +121,30 @@ SessionStartup.prototype = {
       return;
 
     // get string containing session state
-    this._iniString = this._readStateFile(sessionFile);
+    let iniString = this._readStateFile(sessionFile);
-    if (!this._iniString)
+    if (!iniString)
       return;
 
     // parse the session state into a JS object
-    let initialState;
     try {
       // remove unneeded braces (added for compatibility with Firefox 2.0 and 3.0)
-      if (this._iniString.charAt(0) == '(')
+      if (iniString.charAt(0) == '(')
-        this._iniString = this._iniString.slice(1, -1);
+        iniString = iniString.slice(1, -1);
       try {
-        initialState = JSON.parse(this._iniString);
+        this._initialState = JSON.parse(iniString);
       }
       catch (exJSON) {
         var s = new Cu.Sandbox("about:blank");
-        initialState = Cu.evalInSandbox("(" + this._iniString + ")", s);
+        this._initialState = Cu.evalInSandbox("(" + iniString + ")", s);
-        this._iniString = JSON.stringify(initialState);
       }
     }
     catch (ex) { debug("The session file is invalid: " + ex); }
 
     let resumeFromCrash = prefBranch.getBoolPref("sessionstore.resume_from_crash");
     let lastSessionCrashed =
-      initialState && initialState.session && initialState.session.state &&
+      this._initialState && this._initialState.session &&
-      initialState.session.state == STATE_RUNNING_STR;
+      this._initialState.session.state &&
+      this._initialState.session.state == STATE_RUNNING_STR;
 
     // Report shutdown success via telemetry. Shortcoming here are
     // being-killed-by-OS-shutdown-logic, shutdown freezing after
@@ -158,17 +157,17 @@ SessionStartup.prototype = {
       this._sessionType = Ci.nsISessionStartup.RECOVER_SESSION;
     else if (!lastSessionCrashed && doResumeSession)
       this._sessionType = Ci.nsISessionStartup.RESUME_SESSION;
-    else if (initialState)
+    else if (this._initialState)
       this._sessionType = Ci.nsISessionStartup.DEFER_SESSION;
     else
-      this._iniString = null; // reset the state string
+      this._initialState = null; // reset the state
 
     // wait for the first browser window to open
     // Don't reset the initial window's default args (i.e. the home page(s))
     // if all stored tabs are pinned.
     if (this.doRestore() &&
-        (!initialState.windows ||
+        (!this._initialState.windows ||
-        !initialState.windows.every(function (win)
+        !this._initialState.windows.every(function (win)
            win.tabs.every(function (tab) tab.pinned))))
       Services.obs.addObserver(this, "domwindowopened", true);
 
@@ -204,8 +203,8 @@ SessionStartup.prototype = {
       break;
     case "sessionstore-windows-restored":
       Services.obs.removeObserver(this, "sessionstore-windows-restored");
-      // free _iniString after nsSessionStore is done with it
+      // free _initialState after nsSessionStore is done with it
-      this._iniString = null;
+      this._initialState = null;
       this._sessionType = Ci.nsISessionStartup.NO_SESSION;
       break;
     }
@@ -254,7 +253,7 @@ SessionStartup.prototype = {
    * Get the session state as a string
    */
   get state() {
-    return this._iniString;
+    return this._initialState;
   },
 
   /**

browser/components/sessionstore/src/nsSessionStore.js

@@ -304,33 +304,31 @@ SessionStoreService.prototype = {
     this._sessionFileBackup.append("sessionstore.bak");
 
     // get string containing session state
-    var iniString;
     var ss = Cc["@mozilla.org/browser/sessionstartup;1"].
              getService(Ci.nsISessionStartup);
     try {
       if (ss.doRestore() ||
           ss.sessionType == Ci.nsISessionStartup.DEFER_SESSION)
-        iniString = ss.state;
+        this._initialState = ss.state;
     }
     catch(ex) { dump(ex + "\n"); } // no state to restore, which is ok
 
-    if (iniString) {
+    if (this._initialState) {
       try {
         // If we're doing a DEFERRED session, then we want to pull pinned tabs
         // out so they can be restored.
         if (ss.sessionType == Ci.nsISessionStartup.DEFER_SESSION) {
-          let [iniState, remainingState] = this._prepDataForDeferredRestore(iniString);
+          let [iniState, remainingState] = this._prepDataForDeferredRestore(this._initialState);
           // If we have a iniState with windows, that means that we have windows
           // with app tabs to restore.
           if (iniState.windows.length)
             this._initialState = iniState;
+          else
+            this._initialState = null;
           if (remainingState.windows.length)
             this._lastSessionState = remainingState;
         }
         else {
-          // parse the session state into JS objects
-          this._initialState = JSON.parse(iniString);
-
           let lastSessionCrashed =
             this._initialState.session && this._initialState.session.state &&
             this._initialState.session.state == STATE_RUNNING_STR;
@@ -342,7 +340,7 @@ SessionStoreService.prototype = {
               // replace the crashed session with a restore-page-only session
               let pageData = {
                 url: "about:sessionrestore",
-                formdata: { "#sessionData": iniString }
+                formdata: { "#sessionData": JSON.stringify(this._initialState) }
               };
               this._initialState = { windows: [{ tabs: [{ entries: [pageData] }] }] };
             }
@@ -811,7 +809,7 @@ SessionStoreService.prototype = {
           // We'll cheat a little bit and reuse _prepDataForDeferredRestore
           // even though it wasn't built exactly for this.
           let [appTabsState, normalTabsState] =
-            this._prepDataForDeferredRestore(JSON.stringify({ windows: [closedWindowState] }));
+            this._prepDataForDeferredRestore({ windows: [closedWindowState] });
 
           // These are our pinned tabs, which we should restore
           if (appTabsState.windows.length) {
@@ -3794,12 +3792,11 @@ SessionStoreService.prototype = {
    * this._lastSessionState and will be kept in case the user explicitly wants
    * to restore the previous session (publicly exposed as restoreLastSession).
    *
-   * @param stateString
+   * @param state
-   *        The state string, presumably from nsISessionStartup.state
+   *        The state, presumably from nsISessionStartup.state
    * @returns [defaultState, state]
    */
-  _prepDataForDeferredRestore: function sss__prepDataForDeferredRestore(stateString) {
+  _prepDataForDeferredRestore: function sss__prepDataForDeferredRestore(state) {
-    let state = JSON.parse(stateString);
     let defaultState = { windows: [], selectedWindow: 1 };
 
     state.selectedWindow = state.selectedWindow || 1;