Remove extension group from DOMWrapperWorld.

extensions/renderer/test_extensions_renderer_client.cc

Index: extensions/renderer/test_extensions_renderer_client.cc
diff --git a/extensions/renderer/test_extensions_renderer_client.cc b/extensions/renderer/test_extensions_renderer_client.cc
index 5299878ac8aa072abf43f1b1fcdfdf8c35ac6a31..31c74a40ae3ea6337e28dac826079aee9330a193 100644
--- a/extensions/renderer/test_extensions_renderer_client.cc
+++ b/extensions/renderer/test_extensions_renderer_client.cc
@@ -6,9 +6,13 @@
 
 namespace extensions {
 
-TestExtensionsRendererClient::TestExtensionsRendererClient() {}
+TestExtensionsRendererClient::TestExtensionsRendererClient() {
+  ExtensionsRendererClient::Set(this);
+}
 
-TestExtensionsRendererClient::~TestExtensionsRendererClient() {}
+TestExtensionsRendererClient::~TestExtensionsRendererClient() {
+  ExtensionsRendererClient::Set(nullptr);
+}
 
 bool TestExtensionsRendererClient::IsIncognitoProcess() const {
   return false;