Bug 1730287. Fix startup.first_run_is_from_dmg telemetry to report first-run-not-from-dmg stats. r=mstange

Differential Revision: https://phabricator.services.mozilla.com/D125301

toolkit/xre/MacRunFromDmgUtils.mm

@@ -356,13 +356,14 @@ bool MaybeInstallFromDmgAndRelaunch() {
   NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
 
   @autoreleasepool {
-    if (!IsAppRunningFromDmg()) {
+    bool isFromDmg = IsAppRunningFromDmg();
+
+    Telemetry::ScalarSet(Telemetry::ScalarID::STARTUP_FIRST_RUN_IS_FROM_DMG, isFromDmg);
+
+    if (!isFromDmg) {
       return false;
     }
 
-    Telemetry::ScalarSet(Telemetry::ScalarID::STARTUP_FIRST_RUN_IS_FROM_DMG,
-                         MacRunFromDmgUtils::IsAppRunningFromDmg());
-
     // The Applications directory may not be at /Applications, although in
     // practice we're unlikely to encounter since run-from-.dmg is really an
     // issue with novice mac users. Still, look it up correctly: