Bug 665260 - Store start time in sessionstore data [r=dietrich]

browser/components/sessionstore/src/nsSessionStore.js

@@ -198,6 +198,10 @@ SessionStoreService.prototype = {
   // time in milliseconds (Date.now()) when the session was last written to file
   _lastSaveTime: 0,
 
+  // time in milliseconds when the session was started (saved across sessions),
+  // defaults to now if no session was restored or timestamp doesn't exist
+  _sessionStartTime: Date.now(),
+
   // states for all currently opened windows
   _windows: {},
 
@@ -344,6 +348,11 @@ SessionStoreService.prototype = {
             }
           }
 
+          // Load the session start time from the previous state
+          this._sessionStartTime = this._initialState.session &&
+                                   this._initialState.session.startTime ||
+                                   this._sessionStartTime;
+
           // make sure that at least the first window doesn't have anything hidden
           delete this._initialState.windows[0].hidden;
           // Since nothing is hidden in the first window, it cannot be a popup
@@ -1509,9 +1518,13 @@ SessionStoreService.prototype = {
       this._closedWindows = this._closedWindows.concat(lastSessionState._closedWindows);
       this._capClosedWindows();
     }
-    // Set recent crashes
+
+    // Set data that persists between sessions
     this._recentCrashes = lastSessionState.session &&
                           lastSessionState.session.recentCrashes || 0;
+    this._sessionStartTime = lastSessionState.session &&
+                             lastSessionState.session.startTime ||
+                             this._sessionStartTime;
 
     this._lastSessionState = null;
   },
@@ -3420,7 +3433,8 @@ SessionStoreService.prototype = {
 
     oState.session = {
       state: this._loadState == STATE_RUNNING ? STATE_RUNNING_STR : STATE_STOPPED_STR,
-      lastUpdate: Date.now()
+      lastUpdate: Date.now(),
+      startTime: this._sessionStartTime
     };
     if (this._recentCrashes)
       oState.session.recentCrashes = this._recentCrashes;