fixup! Bug 9173: Change the default Firefox profile directory to be relative.

Bug 42519: Disable portable mode also if is-packaged-app is present.

That is the file Firefox uses for .deb packages.

toolkit/xre/nsXREDirProvider.cpp

@@ -1282,20 +1282,31 @@ nsresult nsXREDirProvider::GetPortableDataDir(nsIFile** aFile,
   }
 #  endif
 
+#  if defined(MOZ_WIDGET_GTK)
+  // On Linux, Firefox supports the is-packaged-app for the .deb distribution.
+  // We cannot use mozilla::widget::IsPackagedAppFileExists because it relies on
+  // this service to be initialized, but this function is called during the
+  // initialization. Therefore, we need to re-implement this check.
+  nsLiteralCString systemInstallNames[] = {"system-install"_ns,
+                                           "is-packaged-app"_ns};
+#  else
+  nsLiteralCString systemInstallNames[] = {"system-install"_ns};
+#  endif
+  for (const nsLiteralCString& fileName : systemInstallNames) {
     nsCOMPtr<nsIFile> systemInstallFile;
     rv = exeDir->Clone(getter_AddRefs(systemInstallFile));
     NS_ENSURE_SUCCESS(rv, rv);
-  rv = systemInstallFile->AppendNative("system-install"_ns);
+    rv = systemInstallFile->AppendNative(fileName);
     NS_ENSURE_SUCCESS(rv, rv);
 
     bool exists = false;
     rv = systemInstallFile->Exists(&exists);
     NS_ENSURE_SUCCESS(rv, rv);
     if (exists) {
-    aIsPortable = false;
       gDataDirPortable.emplace(nullptr);
       return NS_OK;
     }
+  }
 
   nsCOMPtr<nsIFile> localDir = exeDir;
 #  if defined(XP_MACOSX)

xpcom/io/nsAppFileLocationProvider.cpp

@@ -195,10 +195,18 @@ static nsresult SetupPortableMode(nsIFile** aDirectory, bool aLocal,
   }
 #  endif
 
+#  if defined(MOZ_WIDGET_GTK)
+  // On Linux, Firefox supports the is-packaged-app for the .deb distribution.
+  nsLiteralCString systemInstallNames[] = {"system-install"_ns,
+                                           "is-packaged-app"_ns};
+#  else
+  nsLiteralCString systemInstallNames[] = {"system-install"_ns};
+#  endif
+  for (const nsLiteralCString& fileName : systemInstallNames) {
     nsCOMPtr<nsIFile> systemInstallFile;
     rv = exeDir->Clone(getter_AddRefs(systemInstallFile));
     NS_ENSURE_SUCCESS(rv, rv);
-  rv = systemInstallFile->AppendNative("system-install"_ns);
+    rv = systemInstallFile->AppendNative(fileName);
     NS_ENSURE_SUCCESS(rv, rv);
 
     bool exists = false;
@@ -208,6 +216,7 @@ static nsresult SetupPortableMode(nsIFile** aDirectory, bool aLocal,
       aIsPortable = false;
       return NS_OK;
     }
+  }
 
   nsCOMPtr<nsIFile> localDir = exeDir;
 #  if defined(XP_MACOSX)
@@ -226,6 +235,7 @@ static nsresult SetupPortableMode(nsIFile** aDirectory, bool aLocal,
     NS_ENSURE_SUCCESS(rv, rv);
   }
 
+  bool exists = false;
   rv = localDir->Exists(&exists);
   NS_ENSURE_SUCCESS(rv, rv);
   if (!exists) {