sync: Refactor StatusChangeChecker hierarchy

chrome/browser/sync/test/integration/status_change_checker.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_SYNC_TEST_INTEGRATION_STATUS_CHANGE_CHECKER_H_
 #define CHROME_BROWSER_SYNC_TEST_INTEGRATION_STATUS_CHANGE_CHECKER_H_
 
 #include <string>
 
+#include "base/time/time.h"
+
 class ProfileSyncServiceHarness;
 
-// Interface for a helper class that can be used to check if a desired change in
-// the state of the sync engine has taken place. Used by the desktop sync
-// integration tests.
+// Interface for a helper class that can pump the message loop while waiting
+// for a certain state transition to take place.
 //
-// Usage: Tests that want to use this class to wait for an arbitrary sync state
-// must implement a concrete StatusChangeChecker object and pass it to
-// ProfileSyncServiceHarness::AwaitStatusChange().
+// This is a template that should be filled in by child classes so they can
+// observe specific kinds of changes and await specific conditions.
+//
+// The instances of this class are intended to be single-use.  It doesn't make
+// sense to call StartBlockingWait() more than once.
 class StatusChangeChecker {
  public:
   explicit StatusChangeChecker();
 
-  // Called every time ProfileSyncServiceHarness is notified of a change in the
-  // state of the sync engine. Returns true if the desired change has occurred.
-  virtual bool IsExitConditionSatisfied() = 0;
-
   // Returns a string representing this current StatusChangeChecker, and
   // possibly some small part of its state.  For example: "AwaitPassphraseError"
   // or "AwaitMigrationDone(BOOKMARKS)".
   virtual std::string GetDebugMessage() const = 0;
 
+  // Returns true if the blocking wait was exited because of a timeout.
+  bool TimedOut() const;
+
+  virtual bool IsExitConditionSatisfied() = 0;
+
  protected:
   virtual ~StatusChangeChecker();
+
+  // Timeout length when blocking.
+  virtual base::TimeDelta GetTimeoutDuration();
+
+  // Helper function to start running the nested message loop.
+  //
+  // Will exit if IsExitConditionSatisfied() returns true when called from
+  // CheckExitCondition(), if a timeout occurs, or if StopWaiting() is called.
+  //
+  // The timeout length is specified with GetTimeoutDuration().
+  void StartBlockingWait();
+
+  // Stop the nested running of the message loop started in StartBlockingWait().
+  void StopWaiting();
+
+  // Checks IsExitConditionSatisfied() and calls StopWaiting() if it returns
+  // true.
+  void CheckExitCondition();
+
+  // Called when the blocking wait timeout is exceeded.
+  void OnTimeout();
+
+  bool timed_out_;
+  bool wait_started_;
 };
 
 #endif  // CHROME_BROWSER_SYNC_TEST_INTEGRATION_STATUS_CHANGE_CHECKER_H_