Introduce IEImporterTestRegistryOverrider to be able to override the registry for a test and flag t…

chrome/browser/importer/ie_importer_test_registry_overrider_win.cc

+// Copyright (c) 2013 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/importer/ie_importer_test_registry_overrider_win.h"
+
+#include <windows.h>
+
+#include <string>
+
+#include "base/environment.h"
+#include "base/guid.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/utf_string_conversions.h"
+#include "base/win/registry.h"
+
+namespace {
+
+// The key to which a random subkey will be appended. This key itself will never
+// be deleted.
+const wchar_t kTestHKCUOverrideKey[] = L"SOFTWARE\\Chromium Unit Tests";
+const char kTestHKCUOverrideEnvironmentVariable[] =
+    "IE_IMPORTER_TEST_OVERRIDE_HKCU";
+
+base::string16 GetTestKeyFromSubKey(const base::string16& subkey) {
+  base::string16 key(kTestHKCUOverrideKey);
+  key.push_back(L'\\');
+  key.append(subkey);
+  return key;
+}
+
+bool GetSubKeyFromEnvironment(base::string16* subkey) {
+  scoped_ptr<base::Environment> env(base::Environment::Create());
+  std::string value;
+  bool result = env->GetVar(kTestHKCUOverrideEnvironmentVariable, &value);
+  if (result && subkey)
+    *subkey = UTF8ToUTF16(value);
+  return result;
+}
+
+}  // namespace
+
+////////////////////////////////////////////////////////////////////////////////
+// IEImporterTestRegistryOverrider, public:
+
+IEImporterTestRegistryOverrider::IEImporterTestRegistryOverrider()
+    : override_performed_(false), override_initiated_(false) {
+}
+
+IEImporterTestRegistryOverrider::~IEImporterTestRegistryOverrider() {
+  base::AutoLock auto_lock(lock_.Get());
+  if (override_performed_) {
+    override_active_in_process_ = false;
+
+    DWORD result = RegOverridePredefKey(HKEY_CURRENT_USER, NULL);
+    DLOG_IF(ERROR, result != ERROR_SUCCESS)
+        << "Failed to unset current override";
+
+    if (override_initiated_) {
+      base::string16 subkey;
+      if (!GetSubKeyFromEnvironment(&subkey)) {
+        NOTREACHED();
+      } else {
+        base::string16 key(GetTestKeyFromSubKey(subkey));
+        base::win::RegKey reg_key(HKEY_CURRENT_USER, key.c_str(),
+                                  KEY_ALL_ACCESS);
+        DCHECK(reg_key.Valid());
+        reg_key.DeleteKey(L"");
+      }
+
+      scoped_ptr<base::Environment> env(base::Environment::Create());
+      env->UnSetVar(kTestHKCUOverrideEnvironmentVariable);
+    }
+  }
+}
+
+bool IEImporterTestRegistryOverrider::SetRegistryOverride() {
+  base::AutoLock auto_lock(lock_.Get());
+  DCHECK(!GetSubKeyFromEnvironment(NULL));
+  override_initiated_ = true;
+  scoped_ptr<base::Environment> env(base::Environment::Create());
+  const base::string16 random_subkey(UTF8ToUTF16(base::GenerateGUID()));
+  return StartRegistryOverride(random_subkey) &&
+      env->SetVar(kTestHKCUOverrideEnvironmentVariable,
+                  UTF16ToUTF8(random_subkey));
+}
+
+bool IEImporterTestRegistryOverrider::StartRegistryOverrideIfNeeded() {
+  base::string16 subkey;
+  if (!GetSubKeyFromEnvironment(&subkey))

[robertshield, 2013/05/03 13:52:37]

why is it safe to not have this line protected by the lock?

[gab, 2013/05/03 14:49:10]

Done.

+    return true;
+
+  base::AutoLock auto_lock(lock_.Get());
+  return StartRegistryOverride(subkey);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// IEImporterTestRegistryOverrider, private:
+
+bool IEImporterTestRegistryOverrider::StartRegistryOverride(
+    const base::string16& subkey) {
+  lock_.Get().AssertAcquired();
+  // Override the registry whether |override_active_in_process_| or not as some

[robertshield, 2013/05/03 13:52:37]

It seems like it would be better to allow only a single instance of this class
to be performing process-wide registry overrides at once.

[gab, 2013/05/03 14:49:10]

Not doing this as per F2F discussion.

+  // Windows API calls seem to reset the override. However, make sure to undo

[robertshield, 2013/05/03 13:52:37]

which API calls reset the override? If the override can be spuriously reset,
then this won't help. 

[gab, 2013/05/03 14:49:10]

Seems to be IUrlHistoryStg2::AddUrl (as per the comment on a call removed in
this CL in ie_importer_browsertest_win.cc).

+  // any existing override as this method will otherwise generate a fake key
+  // within the current fake key.
+  DWORD result = RegOverridePredefKey(HKEY_CURRENT_USER, NULL);
+  DLOG_IF(ERROR, result != ERROR_SUCCESS) << "Failed to unset current override";
+
+  const base::string16 key(GetTestKeyFromSubKey(subkey));
+  base::win::RegKey temp_hkcu_hive_key;
+  result = temp_hkcu_hive_key.Create(HKEY_CURRENT_USER, key.c_str(),
+                                     KEY_ALL_ACCESS);
+  if (result != ERROR_SUCCESS || !temp_hkcu_hive_key.Valid()) {
+    DPLOG(ERROR) << result;
+    return false;
+  }
+
+  if (!override_active_in_process_) {
+    // Only take ownership of the override if it wasn't already set in this
+    // process.
+    override_performed_ = true;
+    override_active_in_process_ = true;
+  }
+  return RegOverridePredefKey(HKEY_CURRENT_USER,
+                              temp_hkcu_hive_key.Handle()) == ERROR_SUCCESS;
+}
+
+// static
+bool IEImporterTestRegistryOverrider::override_active_in_process_ = false;
+
+// static
+base::LazyInstance<base::Lock>::Leaky IEImporterTestRegistryOverrider::lock_ =
+    LAZY_INSTANCE_INITIALIZER;