Enable printers sync_integration_tests on chromeos

chrome/browser/sync/test/integration/printers_helper.cc

 // Copyright 2017 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 "chrome/browser/sync/test/integration/printers_helper.h"
 
 #include <algorithm>
 #include <string>
 #include <unordered_map>
 #include <utility>
 #include <vector>
 
 #include "base/memory/ptr_util.h"
 #include "base/run_loop.h"
 #include "base/strings/stringprintf.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "chrome/browser/chromeos/printing/printers_manager.h"
 #include "chrome/browser/chromeos/printing/printers_manager_factory.h"
 #include "chrome/browser/sync/test/integration/sync_datatype_helper.h"
 #include "chrome/browser/sync/test/integration/sync_test.h"
+#include "content/public/browser/browser_thread.h"
 
 using sync_datatype_helper::test;
 
 namespace printers_helper {
 
 namespace {
 
 using PrinterList = std::vector<std::unique_ptr<chromeos::Printer>>;
 
 // Returns true if Printer#id, Printer#description, and Printer#uri all match.
@@ skipping 28 matching lines @@
     map_b.erase(it);
   }
 
   return map_b.empty();
 }
 
 std::string PrinterId(int index) {
   return base::StringPrintf("printer%d", index);
 }
 
+void WaitForTaskCompletion() {
+  // Since PrintersManagerFactory::BuildServiceInstanceFor() uses
+  // content::BrowserThread::GetBlockingPool() to schedule tasks, tests need to

[skym, 2017/04/06 21:03:03]

So what if the PrintersManagerFactory schedules tasks to
BrowserThread::GetBlockingPool()? Why does this integration test care about
waiting for them?

[Gang Wu, 2017/04/06 21:50:56]

Done.

+  // Wait for tasks running on content::BrowserThread::GetBlockingPool() to be

[skym, 2017/04/06 21:03:03]

Wait shouldn't be capitalized

[Gang Wu, 2017/04/06 21:50:56]

Done.

+  // completed and sent replay to UI thread.
+  content::BrowserThread::GetBlockingPool()->FlushForTesting();
+  // Wait for UI thread task completion.

[skym, 2017/04/06 21:03:03]

Can you elaborate what's going on here? What's being posted to the UI thread?
Why do we need to wait for it?

[Gang Wu, 2017/04/06 21:50:56]

Done.

+  base::RunLoop().RunUntilIdle();
+}
+
 }  // namespace
 
 void AddPrinter(chromeos::PrintersManager* manager,
                 const chromeos::Printer& printer) {
   manager->RegisterPrinter(base::MakeUnique<chromeos::Printer>(printer));
 }
 
 void RemovePrinter(chromeos::PrintersManager* manager, int index) {
   chromeos::Printer testPrinter(CreateTestPrinter(index));
   manager->RemovePrinter(testPrinter.id());
@@ skipping 22 matching lines @@
 chromeos::Printer CreateTestPrinter(int index) {
   chromeos::Printer printer(PrinterId(index));
   printer.set_description("Description");
   printer.set_uri(base::StringPrintf("ipp://192.168.1.%d", index));
 
   return printer;
 }
 
 chromeos::PrintersManager* GetVerifierPrinterStore() {
   chromeos::PrintersManager* manager =
       chromeos::PrintersManagerFactory::GetForBrowserContext(

[skym, 2017/04/06 21:03:03]

It seems like there's more stuff that can be moved into the shared function.

[Gang Wu, 2017/04/06 21:50:56]

Done.

           sync_datatype_helper::test()->verifier());
   // Must wait for ModelTypeStore initialization.
-  base::RunLoop().RunUntilIdle();
+  WaitForTaskCompletion();

[skym, 2017/04/06 21:03:03]

Does this really need to be called on every GetVerifierPrinterStore()?

[Gang Wu, 2017/04/06 21:50:56]

no, just first one. but I think there is no harm to wait more times.

[skym, 2017/04/06 22:52:11]

I don't think I agree there is no harm done, but I've probably bikeshedded long
enough on this code review.

 
   return manager;
 }
 
 chromeos::PrintersManager* GetPrinterStore(int index) {
   chromeos::PrintersManager* manager =
       chromeos::PrintersManagerFactory::GetForBrowserContext(
           sync_datatype_helper::test()->GetProfile(index));
   // Must wait for ModelTypeStore initialization.
-  base::RunLoop().RunUntilIdle();
+  WaitForTaskCompletion();
 
   return manager;
 }
 
 int GetVerifierPrinterCount() {
   return GetVerifierPrinterStore()->GetPrinters().size();
 }
 
 int GetPrinterCount(int index) {
   return GetPrinterStore(index)->GetPrinters().size();
@@ skipping 18 matching lines @@
 }
 
 PrintersMatchChecker::PrintersMatchChecker()
     : AwaitMatchStatusChangeChecker(
           base::Bind(&printers_helper::AllProfilesContainSamePrinters),
           "All printers match") {}
 
 PrintersMatchChecker::~PrintersMatchChecker() {}
 
 }  // namespace printers_helper