Introduce ThreadTaskRunnerHandle::OverrideForTesting and TestMockTimeTaskRunner::ScopedContext.

chrome/browser/chromeos/policy/server_backed_state_keys_broker.h

Index: chrome/browser/chromeos/policy/server_backed_state_keys_broker.h
diff --git a/chrome/browser/chromeos/policy/server_backed_state_keys_broker.h b/chrome/browser/chromeos/policy/server_backed_state_keys_broker.h
index de4baf79b1af3ca7eee20f3619c647a391c555c8..0c987cf730bce0e534113664fd3bdaf58359a78f 100644
--- a/chrome/browser/chromeos/policy/server_backed_state_keys_broker.h
+++ b/chrome/browser/chromeos/policy/server_backed_state_keys_broker.h
@@ -12,13 +12,8 @@
 #include "base/callback.h"
 #include "base/callback_list.h"
 #include "base/macros.h"
-#include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 
-namespace base {
-class TaskRunner;
-}
-
 namespace chromeos {
 class SessionManagerClient;
 }
@@ -36,8 +31,7 @@ class ServerBackedStateKeysBroker {
       StateKeysCallback;
 
   ServerBackedStateKeysBroker(
-      chromeos::SessionManagerClient* session_manager_client,
-      scoped_refptr<base::TaskRunner> delayed_task_runner);
+      chromeos::SessionManagerClient* session_manager_client);
   ~ServerBackedStateKeysBroker();
 
   // Registers a callback to be invoked whenever the state keys get updated.
@@ -54,6 +48,8 @@ class ServerBackedStateKeysBroker {
   // invoked. See http://crbug.com/649422 for more context.
   void RequestStateKeys(const StateKeysCallback& callback);
 
+  static base::TimeDelta GetPollIntervalForTesting();
+
   // Get the set of current state keys. Empty if state keys are unavailable
   // or pending retrieval.
   const std::vector<std::string>& state_keys() const { return state_keys_; }
@@ -79,8 +75,6 @@ class ServerBackedStateKeysBroker {
 
   chromeos::SessionManagerClient* session_manager_client_;
 
-  scoped_refptr<base::TaskRunner> delayed_task_runner_;
-
   // The current set of state keys.
   std::vector<std::string> state_keys_;