Adds tests for passing and returning null strings to and from the methods of injected Java objects

Bug: 5222742
Change-Id: Id6222aebce7570b0649cd9cb7f4f16b0f0b640a8
diff --git a/tests/assets/bindings_test.html b/tests/assets/bindings_test.html
index 71f3438..2d20ada 100755
--- a/tests/assets/bindings_test.html
+++ b/tests/assets/bindings_test.html
@@ -7,7 +7,7 @@
 }
 
 function testObjectTypes() {
-  return JNIBindingsTest.testObjectTypes("Foo", "", {"foo":"bar"}, {});
+  return JNIBindingsTest.testObjectTypes("Foo", "", null, {"foo":"bar"}, {});
 }
 
 function testArray() {
@@ -104,6 +104,12 @@
     return false;
   }
 
+  returned = JNIBindingsTest.returnNullString();
+  if (returned !== undefined) {
+    appendLog("returnNullString() failed: expected undefined, got " + returned);
+    return false;
+  }
+
   returned = JNIBindingsTest.returnObject();
   if (returned == null) {
     appendLog("returnObject() failed: expected non-null, got " + returned);