Bug 1511714 - Unbreak on platform without GeckoProfiler after bug 1509571. r=mconley

browser/components/sessionstore/StartupPerformance.jsm

@@ -76,7 +76,9 @@ var StartupPerformance = {
   // Record the start timestamp, setup the timer and `this._promiseFinished`.
   // Behavior is unspecified if there was already an ongoing measure.
   _onRestorationStarts(isAutoRestore) {
-    Services.profiler.AddMarker("_onRestorationStarts");
+    if (Services.profiler) {
+      Services.profiler.AddMarker("_onRestorationStarts");
+    }
     this._latestRestoredTimeStamp = this._startTimeStamp = Date.now();
     this._totalNumberOfEagerTabs = 0;
     this._totalNumberOfTabs = 0;
@@ -199,7 +201,9 @@ var StartupPerformance = {
             // to the user switching to a lazily restored tab, or for tabs
             // that are restoring eagerly.
             if (!event.detail.isRemotenessUpdate) {
-              Services.profiler.AddMarker("SSTabRestored");
+              if (Services.profiler) {
+                Services.profiler.AddMarker("SSTabRestored");
+              }
               this._latestRestoredTimeStamp = Date.now();
               this._totalNumberOfEagerTabs += 1;
             }