Fix some leaks and failures under valgrind in JS extensions unit tests.

extensions/renderer/api_test_base.cc

Index: extensions/renderer/api_test_base.cc
diff --git a/extensions/renderer/api_test_base.cc b/extensions/renderer/api_test_base.cc
index f0943c97fa75fba7aa90aa602be0236f7bc6e82f..96ad01b7f08a892eda6936f430303553ca79c092 100644
--- a/extensions/renderer/api_test_base.cc
+++ b/extensions/renderer/api_test_base.cc
@@ -107,6 +107,11 @@ void ApiTestBase::SetUp() {
   RegisterModules();
 }
 
+void ApiTestBase::TearDown() {
+  env()->context()->DispatchOnUnloadEvent();
+  ModuleSystemTest::TearDown();
+}
+
 void ApiTestBase::RegisterModules() {
   v8_schema_registry_.reset(new V8SchemaRegistry);
   const std::vector<std::pair<std::string, int> > resources =