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 73 matching lines @@
   printer.set_uri(base::StringPrintf("ipp://192.168.1.%d", index));
 
   return printer;
 }
 
 chromeos::PrintersManager* GetVerifierPrinterStore() {
   chromeos::PrintersManager* manager =
       chromeos::PrintersManagerFactory::GetForBrowserContext(
           sync_datatype_helper::test()->verifier());
   // Must wait for ModelTypeStore initialization.
+  // Flush here since PrintersManagerFactory::BuildServiceInstanceFor() uses

[skym, 2017/04/06 16:48:44]

Can you expand on this comment. Why are we flushing? You're explaining why
you've chosen this particular BlockingPool, but not why flushing is
important/required.

[Gang Wu, 2017/04/06 19:22:59]

Done.

+  // content::BrowserThread::GetBlockingPool().
+  content::BrowserThread::GetBlockingPool()->FlushForTesting();

[skym, 2017/04/06 16:48:44]

I don't like how this is being done. Do we really need to flush/run until idle
before every PrintersManager access? Can this just be done once at the start of
each test case? Or even better, inside SetupSync()?

[Gang Wu, 2017/04/06 19:22:59]

Done.

   base::RunLoop().RunUntilIdle();
 
   return manager;
 }
 
 chromeos::PrintersManager* GetPrinterStore(int index) {

[skym, 2017/04/06 16:48:44]

This function looks really similar to the above one. Maybe some simple
refactoring is in order?

[Gang Wu, 2017/04/06 19:22:59]

Done.

   chromeos::PrintersManager* manager =
       chromeos::PrintersManagerFactory::GetForBrowserContext(
           sync_datatype_helper::test()->GetProfile(index));
   // Must wait for ModelTypeStore initialization.
+  // Flush here since PrintersManagerFactory::BuildServiceInstanceFor() uses
+  // content::BrowserThread::GetBlockingPool().
+  content::BrowserThread::GetBlockingPool()->FlushForTesting();
   base::RunLoop().RunUntilIdle();
 
   return manager;
 }
 
 int GetVerifierPrinterCount() {
   return GetVerifierPrinterStore()->GetPrinters().size();
 }
 
 int GetPrinterCount(int index) {
@@ skipping 19 matching lines @@
 }
 
 PrintersMatchChecker::PrintersMatchChecker()
     : AwaitMatchStatusChangeChecker(
           base::Bind(&printers_helper::AllProfilesContainSamePrinters),
           "All printers match") {}
 
 PrintersMatchChecker::~PrintersMatchChecker() {}
 
 }  // namespace printers_helper