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

chrome/browser/sync/test/engine/syncer_command_test.h

Index: chrome/browser/sync/test/engine/syncer_command_test.h
diff --git a/chrome/browser/sync/test/engine/syncer_command_test.h b/chrome/browser/sync/test/engine/syncer_command_test.h
index c6fccbb21e9e5c2d2633a4ada91dbfd5e55c0d72..2b4e17ae07c561eac8e7b73f14ba043bf60ea60f 100644
--- a/chrome/browser/sync/test/engine/syncer_command_test.h
+++ b/chrome/browser/sync/test/engine/syncer_command_test.h
@@ -11,12 +11,15 @@
 #include <vector>
 
 #include "base/compiler_specific.h"
+#include "base/memory/ref_counted.h"
 #include "base/message_loop.h"
+#include "chrome/browser/sync/engine/model_changing_syncer_command.h"
 #include "chrome/browser/sync/engine/model_safe_worker.h"
 #include "chrome/browser/sync/sessions/debug_info_getter.h"
 #include "chrome/browser/sync/sessions/sync_session.h"
 #include "chrome/browser/sync/sessions/sync_session_context.h"
 #include "chrome/browser/sync/test/engine/mock_connection_manager.h"
+#include "chrome/browser/sync/test/engine/fake_model_worker.h"
 #include "chrome/browser/sync/test/engine/test_directory_setter_upper.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/gmock/include/gmock/gmock.h"
@@ -93,6 +96,9 @@ class SyncerCommandTestWithParam : public testing::TestWithParam<T>,
   virtual void SetUp() {
     syncdb_->SetUp();
     ResetContext();
+    // The session always expects there to be a passive worker.
+    workers()->push_back(
+        make_scoped_refptr(new FakeModelWorker(GROUP_PASSIVE)));
   }
   virtual void TearDown() {
     syncdb_->TearDown();
@@ -157,6 +163,41 @@ class SyncerCommandTestWithParam : public testing::TestWithParam<T>,
     return &mock_debug_info_getter_;
   }
 
+  // Helper functions to check command.GetGroupsToChange().
+
+  void ExpectNoGroupsToChange(const ModelChangingSyncerCommand& command) {
+    EXPECT_TRUE(command.GetGroupsToChangeForTest(*session()).empty());
+  }
+
+  void ExpectGroupToChange(
+      const ModelChangingSyncerCommand& command, ModelSafeGroup group) {
+    std::set<ModelSafeGroup> expected_groups_to_change;
+    expected_groups_to_change.insert(group);
+    EXPECT_EQ(expected_groups_to_change,
+              command.GetGroupsToChangeForTest(*session()));
+  }
+
+  void ExpectGroupsToChange(
+      const ModelChangingSyncerCommand& command,
+      ModelSafeGroup group1, ModelSafeGroup group2) {
+    std::set<ModelSafeGroup> expected_groups_to_change;
+    expected_groups_to_change.insert(group1);
+    expected_groups_to_change.insert(group2);
+    EXPECT_EQ(expected_groups_to_change,
+              command.GetGroupsToChangeForTest(*session()));
+  }
+
+  void ExpectGroupsToChange(
+      const ModelChangingSyncerCommand& command,
+      ModelSafeGroup group1, ModelSafeGroup group2, ModelSafeGroup group3) {
+    std::set<ModelSafeGroup> expected_groups_to_change;
+    expected_groups_to_change.insert(group1);
+    expected_groups_to_change.insert(group2);
+    expected_groups_to_change.insert(group3);
+    EXPECT_EQ(expected_groups_to_change,
+              command.GetGroupsToChangeForTest(*session()));
+  }
+
  private:
   MessageLoop message_loop_;
   scoped_ptr<TestDirectorySetterUpper> syncdb_;