Clean up threading model of external extension providers

chrome/browser/extensions/external_pref_extension_loader.cc

+// Copyright (c) 2011 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_pref_extension_loader.h"
+
+#include "app/app_paths.h"
+#include "base/file_path.h"
+#include "base/file_util.h"
+#include "base/logging.h"
+#include "base/path_service.h"
+#include "chrome/browser/browser_thread.h"
+#include "chrome/common/json_value_serializer.h"
+
+namespace {
+
+// Caller takes ownership of the returned dictionary
+DictionaryValue* ExtractPrefs(ValueSerializer* serializer) {
+  std::string error_msg;
+  Value* extensions = serializer->Deserialize(NULL, &error_msg);
+  if (!extensions) {
+    LOG(WARNING) << "Unable to deserialize json data: " << error_msg;
+  } else {
+    if (!extensions->IsType(Value::TYPE_DICTIONARY)) {
+      NOTREACHED() << "Invalid json data";
+    } else {
+      return static_cast<DictionaryValue*>(extensions);
+    }
+  }
+  return new DictionaryValue;
+}
+
+}  // namespace
+
+ExternalPrefExtensionLoader::ExternalPrefExtensionLoader() {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+}
+
+void ExternalPrefExtensionLoader::StartLoading() {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  BrowserThread::PostTask(
+      BrowserThread::FILE, FROM_HERE,
+      NewRunnableMethod(
+          this,
+          &ExternalPrefExtensionLoader::LoadOnFileThread));
+}
+
+void ExternalPrefExtensionLoader::LoadOnFileThread() {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  FilePath json_file;
+  PathService::Get(app::DIR_EXTERNAL_EXTENSIONS, &json_file);
+  json_file = json_file.Append(FILE_PATH_LITERAL("external_extensions.json"));
+  scoped_ptr<DictionaryValue> prefs;
+
+  if (file_util::PathExists(json_file)) {
+    JSONFileValueSerializer serializer(json_file);
+    prefs.reset(ExtractPrefs(&serializer));
+  } else {
+    prefs.reset(new DictionaryValue());
+  }
+
+  prefs_.reset(prefs.release());
+  BrowserThread::PostTask(
+       BrowserThread::UI, FROM_HERE,
+       NewRunnableMethod(
+           this,
+           &ExternalPrefExtensionLoader::LoadFinished));
+}
+
+ExternalTestingExtensionLoader::ExternalTestingExtensionLoader(
+    const std::string& json_data) {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  JSONStringValueSerializer serializer(json_data);
+  testing_prefs_.reset(ExtractPrefs(&serializer));
+}
+
+void ExternalTestingExtensionLoader::StartLoading() {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  prefs_.reset(
+      static_cast<DictionaryValue*>(testing_prefs_->DeepCopy()));
+  LoadFinished();
+}