Bug 1653384: Require MOZ_FORCE_DISABLE_E10S to be set to the current application version. r=froydnj

Depends on D86240

Differential Revision: https://phabricator.services.mozilla.com/D86241

toolkit/xre/nsAppRunner.cpp

@@ -5161,9 +5161,13 @@ bool BrowserTabsRemoteAutostart() {
   }
 
   // Uber override pref for emergency blocking
-  if (gBrowserTabsRemoteAutostart && EnvHasValue("MOZ_FORCE_DISABLE_E10S")) {
-    gBrowserTabsRemoteAutostart = false;
-    status = kE10sForceDisabled;
+  if (gBrowserTabsRemoteAutostart) {
+    const char* forceDisable = PR_GetEnv("MOZ_FORCE_DISABLE_E10S");
+    // The environment variable must match the application version to apply.
+    if (forceDisable && !strcmp(forceDisable, gAppData->version)) {
+      gBrowserTabsRemoteAutostart = false;
+      status = kE10sForceDisabled;
+    }
   }
 
   gBrowserTabsRemoteStatus = status;