Ensure tests have an active task runner

chrome/browser/extensions/activity_log/uma_policy_unittest.cc

Index: chrome/browser/extensions/activity_log/uma_policy_unittest.cc
diff --git a/chrome/browser/extensions/activity_log/uma_policy_unittest.cc b/chrome/browser/extensions/activity_log/uma_policy_unittest.cc
index 86f57f839a0c7723d732bd0fc654b48e469a8765..e7ba924213ecd90e2e8be2ab57edd675a5230d04 100644
--- a/chrome/browser/extensions/activity_log/uma_policy_unittest.cc
+++ b/chrome/browser/extensions/activity_log/uma_policy_unittest.cc
@@ -6,6 +6,7 @@
 #include "chrome/browser/extensions/activity_log/activity_action_constants.h"
 #include "chrome/browser/extensions/activity_log/uma_policy.h"
 #include "chrome/test/base/testing_profile.h"
+#include "content/public/test/test_browser_thread_bundle.h"
 #include "extensions/common/dom_action_types.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -18,6 +19,7 @@ class UmaPolicyTest : public testing::Test {
   }
 
  protected:
+  content::TestBrowserThreadBundle thread_bundle_;
   scoped_ptr<TestingProfile> profile_;
 };