[SyncFS] Refine callback helpers

chrome/browser/sync_file_system/drive_backend/callback_helper_unittest.cc

Index: chrome/browser/sync_file_system/drive_backend/callback_helper_unittest.cc
diff --git a/chrome/browser/sync_file_system/drive_backend/callback_helper_unittest.cc b/chrome/browser/sync_file_system/drive_backend/callback_helper_unittest.cc
index 238d24f2f89bbf64f72d02cabb3d093f6c54b756..00cbb8d7c807bf0ca8ea5b5d71bc4917d9b0bdd3 100644
--- a/chrome/browser/sync_file_system/drive_backend/callback_helper_unittest.cc
+++ b/chrome/browser/sync_file_system/drive_backend/callback_helper_unittest.cc
@@ -27,17 +27,29 @@ void CallbackWithPassed(bool* called, scoped_ptr<int>) {
 
 }  // namespace
 
-TEST(DriveBackendCallbackHelperTest, CreateRelayedCallbackTest) {
+TEST(DriveBackendCallbackHelperTest, RelayCallbackTest) {
   base::MessageLoop message_loop;
 
   bool called = false;
-  CreateRelayedCallback(base::Bind(&SimpleCallback, &called)).Run(0);
+  RelayCallbackToTaskRunner(

[peria, 2014/04/24 07:30:05]

callback_helper.h has 2 interface templates, RelayCallbackToTaskRunner() and
RelayCallbackToCurrentThread().
In addition, we can pass 3 types of functions to them, void(), void(T), and
void(T1, T2).

Please make a test set that can detect which template is wrong.
If #40 fails, we cannot detect whether RelayToTaskRunner<void()> has a bug or
RelayCallbackToTaskRunner() has a bug.

[peria, 2014/04/24 07:30:05]

For example, following combination may detect it.
- RelayCallbackToTaskRunner(void()) : (1)
- RelayCallbackToTaskRunner(void(T))
- RelayCallbackToTaskRunner(void(T,U))
- RelayCallbackToCurrentThread(void()) : comparable with (1)

[tzik, 2014/04/24 07:58:34]

I think testing all possible specialization for each simple class is over
pessimistic.

Anyway I change add a .h.pump to generate each pattern of specialization.
I think it's even less error prone now.

+      base::MessageLoopProxy::current(),
+      FROM_HERE,
+      base::Bind(&SimpleCallback, &called, 0)).Run();
   EXPECT_FALSE(called);
   base::RunLoop().RunUntilIdle();
   EXPECT_TRUE(called);
 
   called = false;
-  CreateRelayedCallback(
+  RelayCallbackToCurrentThread(
+      FROM_HERE,
+      base::Bind(&SimpleCallback, &called)).Run(0);
+  EXPECT_FALSE(called);
+  base::RunLoop().RunUntilIdle();
+  EXPECT_TRUE(called);
+
+  called = false;
+  RelayCallbackToCurrentThread(
+      FROM_HERE,
       base::Bind(&CallbackWithPassed, &called))
       .Run(scoped_ptr<int>(new int));
   EXPECT_FALSE(called);