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

chrome/browser/sync/engine/process_commit_response_command_unittest.cc

 // Copyright (c) 2011 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.
 
 #include <vector>
 
 #include "base/location.h"
 #include "base/stringprintf.h"
 #include "chrome/browser/sync/engine/process_commit_response_command.h"
 #include "chrome/browser/sync/protocol/bookmark_specifics.pb.h"
@@ skipping 35 matching lines @@
     workers()->push_back(
         make_scoped_refptr(new FakeModelWorker(GROUP_DB)));
     workers()->push_back(
         make_scoped_refptr(new FakeModelWorker(GROUP_UI)));
     (*mutable_routing_info())[syncable::BOOKMARKS] = GROUP_UI;
     (*mutable_routing_info())[syncable::PREFERENCES] = GROUP_UI;
     (*mutable_routing_info())[syncable::AUTOFILL] = GROUP_DB;
 
     commit_set_.reset(new sessions::OrderedCommitSet(routing_info()));
     SyncerCommandTestWithParam<T>::SetUp();
+    // Need to explicitly use this-> to avoid obscure template
+    // warning.
+    this->ExpectNoGroupsToChange(command_);
   }
 
  protected:
   using SyncerCommandTestWithParam<T>::context;
   using SyncerCommandTestWithParam<T>::mutable_routing_info;
   using SyncerCommandTestWithParam<T>::routing_info;
   using SyncerCommandTestWithParam<T>::session;
   using SyncerCommandTestWithParam<T>::syncdb;
   using SyncerCommandTestWithParam<T>::workers;
 
@@ skipping 160 matching lines @@
                                 "bookmark 2", syncable::BOOKMARKS);
   CreateUnprocessedCommitResult(pref_id1, id_factory_.root(),
                                 "Pref 1", syncable::PREFERENCES);
   CreateUnprocessedCommitResult(pref_id2, id_factory_.root(),
                                 "Pref 2", syncable::PREFERENCES);
   CreateUnprocessedCommitResult(autofill_id1, id_factory_.root(),
                                 "Autofill 1", syncable::AUTOFILL);
   CreateUnprocessedCommitResult(autofill_id2, id_factory_.root(),
                                 "Autofill 2", syncable::AUTOFILL);
 
+  ExpectGroupsToChange(command_, GROUP_UI, GROUP_DB);
   command_.ExecuteImpl(session());
 
   ScopedDirLookup dir(syncdb()->manager(), syncdb()->name());
   ASSERT_TRUE(dir.good());
   ReadTransaction trans(FROM_HERE, dir);
   Id new_fid;
   ASSERT_TRUE(dir->GetFirstChildId(&trans, id_factory_.root(), &new_fid));
   ASSERT_FALSE(new_fid.IsRoot());
   EXPECT_TRUE(new_fid.ServerKnows());
   EXPECT_FALSE(bookmark_folder_id.ServerKnows());
@@ skipping 71 matching lines @@
     // Alternate between new and old child items, just for kicks.
     Id id = (i % 4 < 2) ? id_factory_.NewLocalId() : id_factory_.NewServerId();
     CreateUnsyncedItem(id, folder_id, base::StringPrintf("Item %d", i),
                        false, syncable::BOOKMARKS, NULL);
   }
 
   // Process the commit response for the parent folder and the first
   // 25 items.  This should apply the values indicated by
   // each CommitResponse_EntryResponse to the syncable Entries.  All new
   // items in the commit batch should have their IDs changed to server IDs.
+  ExpectGroupToChange(command_, GROUP_UI);
   command_.ExecuteImpl(session());
 
   ScopedDirLookup dir(syncdb()->manager(), syncdb()->name());
   ASSERT_TRUE(dir.good());
   ReadTransaction trans(FROM_HERE, dir);
   // Lookup the parent folder by finding a child of the root.  We can't use
   // folder_id here, because it changed during the commit.
   Id new_fid;
   ASSERT_TRUE(dir->GetFirstChildId(&trans, id_factory_.root(), &new_fid));
   ASSERT_FALSE(new_fid.IsRoot());
@@ skipping 84 matching lines @@
 
   // Put some extensions activity in the session.
   {
     ExtensionsActivityMonitor::Records* records =
         session()->mutable_extensions_activity();
     (*records)["ABC"].extension_id = "ABC";
     (*records)["ABC"].bookmark_write_count = 2049U;
     (*records)["xyz"].extension_id = "xyz";
     (*records)["xyz"].bookmark_write_count = 4U;
   }
+  ExpectGroupsToChange(command_, GROUP_UI, GROUP_DB);
   command_.ExecuteImpl(session());
 
   ExtensionsActivityMonitor::Records final_monitor_records;
   context()->extensions_monitor()->GetAndClearRecords(&final_monitor_records);
 
   if (ShouldFailBookmarkCommit()) {
     ASSERT_EQ(2U, final_monitor_records.size())
         << "Should restore records after unsuccessful bookmark commit.";
     EXPECT_EQ("ABC", final_monitor_records["ABC"].extension_id);
     EXPECT_EQ("xyz", final_monitor_records["xyz"].extension_id);
     EXPECT_EQ(2049U, final_monitor_records["ABC"].bookmark_write_count);
     EXPECT_EQ(4U,    final_monitor_records["xyz"].bookmark_write_count);
   } else {
     EXPECT_TRUE(final_monitor_records.empty())
         << "Should not restore records after successful bookmark commit.";
   }
 }
 
 
 }  // namespace browser_sync