Add google-extensions jar so that GoogleLogger class can be used, for
consistency with Google source code.
diff --git a/third_party/BUILD b/third_party/BUILD
index ed7d4c9..f4b88a7 100644
--- a/third_party/BUILD
+++ b/third_party/BUILD
@@ -381,7 +381,11 @@
 
 java_import(
     name = "flogger",
-    jars = ["flogger/flogger-0.3.1.jar", "flogger/flogger-system-backend-0.3.1.jar"]
+    jars = [
+        "flogger/flogger-0.3.1.jar",
+        "flogger/flogger-system-backend-0.3.1.jar",
+        "flogger/google-extensions-0.3.1.jar"
+    ],
 )
 
 java_import(