Add TestBrowserThreadBundle into RenderViewHostTestHarness. Kill some unnecessary real threads.

chrome/browser/extensions/active_tab_unittest.cc

Index: chrome/browser/extensions/active_tab_unittest.cc
diff --git a/chrome/browser/extensions/active_tab_unittest.cc b/chrome/browser/extensions/active_tab_unittest.cc
index 9ca105279c36792504d529054ce92f9df3489e60..0b57f04f9dca79b50ae5374d96aecab52c04d40a 100644
--- a/chrome/browser/extensions/active_tab_unittest.cc
+++ b/chrome/browser/extensions/active_tab_unittest.cc
@@ -54,14 +54,12 @@ scoped_refptr<const Extension> CreateTestExtension(
 }
 
 class ActiveTabTest : public ChromeRenderViewHostTestHarness {
- public:
+ protected:
   ActiveTabTest()
       : extension(CreateTestExtension("deadbeef", true)),
         another_extension(CreateTestExtension("feedbeef", true)),
-        extension_without_active_tab(CreateTestExtension("badbeef", false)),
-        ui_thread_(BrowserThread::UI, base::MessageLoop::current()) {}
+        extension_without_active_tab(CreateTestExtension("badbeef", false)) {}
 
- protected:
   virtual void SetUp() OVERRIDE {
     ChromeRenderViewHostTestHarness::SetUp();
     TabHelper::CreateForWebContents(web_contents());
@@ -124,9 +122,6 @@ class ActiveTabTest : public ChromeRenderViewHostTestHarness {
 
   // An extension without the activeTab permission.
   scoped_refptr<const Extension> extension_without_active_tab;
-
- private:
-  content::TestBrowserThread ui_thread_;
 };
 
 TEST_F(ActiveTabTest, GrantToSinglePage) {