Cleanup PreferenceMACs on browser_tests startup

chrome/test/base/chrome_test_launcher.cc

 // Copyright (c) 2012 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/test/base/chrome_test_launcher.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/command_line.h"
@@ skipping 34 matching lines @@
 
 #if defined(OS_CHROMEOS)
 #include "ash/test/ui_controls_factory_ash.h"
 #endif
 
 #if defined(OS_LINUX) || defined(OS_ANDROID)
 #include "chrome/app/chrome_crash_reporter_client.h"
 #endif
 
 #if defined(OS_WIN)
+#include "base/win/registry.h"
 #include "chrome/app/chrome_crash_reporter_client_win.h"
+#include "chrome/install_static/install_util.h"
 #endif
 
 ChromeTestSuiteRunner::ChromeTestSuiteRunner() {}
 ChromeTestSuiteRunner::~ChromeTestSuiteRunner() {}
 
 int ChromeTestSuiteRunner::RunTestSuite(int argc, char** argv) {
   return ChromeTestSuite(argc, argv).Run();
 }
 
 ChromeTestLauncherDelegate::ChromeTestLauncherDelegate(
@@ skipping 23 matching lines @@
 
   *command_line = new_command_line;
   return true;
 }
 
 content::ContentMainDelegate*
 ChromeTestLauncherDelegate::CreateContentMainDelegate() {
   return new ChromeMainDelegate();
 }
 
+void ChromeTestLauncherDelegate::PreShardingCleanup() {
+#if defined(OS_WIN)
+  // Pre-test cleanup for registry state keyed off the profile dir (which can
+  // proliferate with the use of uniquely named scoped_dirs):
+  // https://crbug.com/721245. This needs to be here in order not to be racy
+  // with any tests that will access that state.
+  base::win::RegKey key(HKEY_CURRENT_USER,
+                        install_static::GetRegistryPath().c_str(),
+                        KEY_SET_VALUE | KEY_QUERY_VALUE);
+  if (key.Valid()) {
+    key.DeleteKey(L"PreferenceMACs");

[jam, 2017/05/17 19:06:16]

does this mean that if someone runs official browser_tests, it will delete this
key for the chrome that the use? that seems bad?

can we only delete the subkeys that have "scoped" in them?

[gab, 2017/05/17 20:01:05]

Yes, but it's not that bad (discussed details offline)
We could but that'd increase complexity where I don't think it's worth it.

+  }
+#endif
+}
+
 int LaunchChromeTests(int default_jobs,
                       content::TestLauncherDelegate* delegate,
                       int argc,
                       char** argv) {
 #if defined(OS_MACOSX)
   chrome_browser_application_mac::RegisterBrowserCrApp();
 #endif
 
 #if defined(OS_WIN)
   // Create a primordial InstallDetails instance for the test.
   install_static::ScopedInstallDetails install_details;
 #endif
 
 #if defined(OS_LINUX) || defined(OS_ANDROID) || defined(OS_WIN)
   // We leak this pointer intentionally. The crash client needs to outlive
   // all other code.
   ChromeCrashReporterClient* crash_client = new ChromeCrashReporterClient();
   ANNOTATE_LEAKING_OBJECT_PTR(crash_client);
   crash_reporter::SetCrashReporterClient(crash_client);
 #endif
 
   return content::LaunchTests(delegate, default_jobs, argc, argv);
 }