Revert 112743 - [Sync] Make syncer commands avoid posting tasks on threads with no work to do

chrome/browser/sync/engine/model_changing_syncer_command.h

Index: chrome/browser/sync/engine/model_changing_syncer_command.h
===================================================================
--- chrome/browser/sync/engine/model_changing_syncer_command.h	(revision 112758)
+++ chrome/browser/sync/engine/model_changing_syncer_command.h	(working copy)
@@ -7,7 +7,6 @@
 #pragma once
 
 #include "base/compiler_specific.h"
-#include "chrome/browser/sync/engine/model_safe_worker.h"
 #include "chrome/browser/sync/engine/syncer_command.h"
 #include "chrome/browser/sync/util/unrecoverable_error_info.h"
 
@@ -42,22 +41,6 @@
     return UnrecoverableErrorInfo();
   }
 
-  std::set<ModelSafeGroup> GetGroupsToChangeForTest(
-      const sessions::SyncSession& session) const {
-    return GetGroupsToChange(session);
-  }
-
- protected:
-  // This should return the set of groups in |session| that need to be
-  // changed.  The returned set should be a subset of
-  // session.GetEnabledGroups().  Subclasses can guarantee this either
-  // by calling one of the session.GetEnabledGroups*() functions and
-  // filtering that, or using GetGroupForModelType() (which handles
-  // top-level/unspecified nodes) to project from model types to
-  // groups.
-  virtual std::set<ModelSafeGroup> GetGroupsToChange(
-      const sessions::SyncSession& session) const = 0;
-
   // Sometimes, a command has work to do that needs to touch global state
   // belonging to multiple ModelSafeGroups, but in a way that is known to be
   // safe.  This will be called once, prior to ModelChangingExecuteImpl,