Fix windows registry loader to carry over prefs from file thread correctly

chrome/browser/extensions/external_registry_loader_win_unittest.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/extensions/external_registry_loader_win.h"
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/run_loop.h"
+#include "base/values.h"
 #include "content/public/test/test_browser_thread_bundle.h"
+#include "extensions/common/value_builder.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace extensions {
 
 namespace {
 
+const char kDummyRegistryKey[] = "dummyId";
+
 class TestExternalRegistryLoader : public ExternalRegistryLoader {
  public:
   TestExternalRegistryLoader() {}
 
   using ExternalRegistryLoader::StartLoading;
 
   void WaitForTwoLoadsToFinished() {
     // Run() returns immediately if Quit() has already been called.
     run_loop_.Run();
   }
 
+  std::vector<int> GetPrefsTestIds() { return prefs_test_ids_; }
+
  private:
   ~TestExternalRegistryLoader() override {}
 
+  std::unique_ptr<base::DictionaryValue> LoadPrefsOnFileThread() override {
+    return DictionaryBuilder().Set(kDummyRegistryKey, id_++).Build();
+  }
   void LoadFinished() override {
     ExternalRegistryLoader::LoadFinished();
     ++load_finished_count_;
     ASSERT_LE(load_finished_count_, 2);
+
+    ASSERT_TRUE(prefs_);
+    int prefs_test_id = -1;
+    EXPECT_TRUE(prefs_->GetInteger(kDummyRegistryKey, &prefs_test_id));
+    prefs_test_ids_.push_back(prefs_test_id);
+
     if (load_finished_count_ == 2)
       run_loop_.Quit();
   }
 
   base::RunLoop run_loop_;
   int load_finished_count_ = 0;
+  int id_ = 0;
+  std::vector<int> prefs_test_ids_;
 
   DISALLOW_COPY_AND_ASSIGN(TestExternalRegistryLoader);
 };
 
 }  // namespace
 
 class ExternalRegistryLoaderUnittest : public testing::Test {
  public:
   ExternalRegistryLoaderUnittest()
       : thread_bundle_(content::TestBrowserThreadBundle::IO_MAINLOOP) {}
@@ skipping 12 matching lines @@
       make_scoped_refptr(new TestExternalRegistryLoader());
 
   test_loader->StartLoading();
   test_loader->StartLoading();
 
   test_loader->WaitForTwoLoadsToFinished();
   // Let registry watcher code complete.
   base::RunLoop().RunUntilIdle();
 }
 
+// Tests that calling StartLoading() twice does not overwrite previous prefs
+// before LoadFinished consumes it.
+// Regression test for https://crbug.com/709304: if two StartLoading() schedules
+// two LoadPrefsOnFileThread, then the second LoadPrefsOnFileThread could
+// overwrite the first one's prefs.
+TEST_F(ExternalRegistryLoaderUnittest, TwoStartLoadingDoesNotOverwritePrefs) {
+  scoped_refptr<TestExternalRegistryLoader> test_loader =
+      make_scoped_refptr(new TestExternalRegistryLoader());
+
+  test_loader->StartLoading();
+  test_loader->StartLoading();
+
+  test_loader->WaitForTwoLoadsToFinished();
+  // Let registry watcher code complete.
+  base::RunLoop().RunUntilIdle();
+
+  std::vector<int> prefs_test_ids = test_loader->GetPrefsTestIds();
+  ASSERT_EQ(2u, prefs_test_ids.size());
+  EXPECT_EQ(0, prefs_test_ids[0]);
+  EXPECT_EQ(1, prefs_test_ids[1]);
+}
+
 }  // namespace extensions