Refactored SettingsFrontend and forwarding of calls to the backends.

chrome/browser/extensions/settings/settings_storage_frontend.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/browser/extensions/settings/settings_storage_frontend.h"
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/file_path.h"
+#include "chrome/browser/extensions/extension_service.h"
+#include "chrome/browser/extensions/settings/settings_backend.h"
+#include "chrome/browser/extensions/settings/settings_storage_quota_enforcer.h"
+#include "chrome/browser/extensions/settings/weak_unlimited_settings_storage.h"
+#include "chrome/common/extensions/extension.h"
+#include "content/public/browser/browser_thread.h"
+
+using content::BrowserThread;
+
+namespace extensions {
+
+namespace {
+

[not at google - send to devlin, 2012/07/18 07:46:18]

Yeah, so I think a lot of this file will change/simplify if the interface is
synchronous (and always expected to be on that the FILE thread).

[Joao da Silva, 2012/07/18 21:40:25]

Yep, managed to do away with the BackendWrapper once every call is guaranteed to
come on FILE.

+void CallbackWithStorage(
+    const std::string& extension_id,
+    const SettingsNamespaceFrontend::StorageCallback& callback,
+    SettingsBackend* backend) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  callback.Run(backend->GetStorage(extension_id));
+}
+
+void CallbackWithUnlimitedStorage(
+    const std::string& extension_id,
+    const SettingsNamespaceFrontend::StorageCallback& callback,
+    SettingsBackend* backend) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  WeakUnlimitedSettingsStorage unlimited_storage(

[not at google - send to devlin, 2012/07/18 07:46:18]

If it's made synchronous then this WeakUnlimited thing needs to go away. I have
no idea why I did that, it's not like the unlimitedStorage permission will
change.

Would need to thread through the unlimitedStorage permission to where it's
created I suppose. Or just thread through the (const) Extension rather than the
extension_id, looks threadsafe to me.

[Joao da Silva, 2012/07/18 21:40:25]

I'm not entirely sure of what you're proposing to do about this. I've kept it
mostly as-is; removing the WeakUnlimitedSettingsStorage decorator would require
some other means of pushing the IGNORE_QUOTA flag into the
SyncableSettingsStorage within the SettingsBackend. I'd rather leave that for
another CL, this one is already large-ish :-)

[not at google - send to devlin, 2012/07/19 06:43:17]

Oh, I remember now. Yeah, ignore this.

+      backend->GetStorage(extension_id));
+  callback.Run(&unlimited_storage);
+}
+
+void DeleteStorageOnFileThread(
+    const std::string& extension_id, SettingsBackend* backend) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  backend->DeleteStorage(extension_id);
+}
+
+}  // namespace
+
+// Ref-counted container for a SettingsBackend object.
+class SettingsStorageFrontend::BackendWrapper
+    : public base::RefCountedThreadSafe<BackendWrapper> {
+ public:
+  // Creates a new BackendWrapper and initializes it on the FILE thread.
+  static scoped_refptr<BackendWrapper> CreateAndInit(
+      const scoped_refptr<SettingsStorageFactory>& factory,
+      const SettingsStorageQuotaEnforcer::Limits& quota,
+      const scoped_refptr<SettingsObserverList>& observers,
+      const FilePath& path) {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+    scoped_refptr<BackendWrapper> backend_wrapper = new BackendWrapper();
+    BrowserThread::PostTask(
+        BrowserThread::FILE, FROM_HERE,
+        base::Bind(
+            &BackendWrapper::InitOnFileThread,
+            backend_wrapper, factory, quota, observers, path));
+    return backend_wrapper;
+  }
+
+  typedef base::Callback<void(SettingsBackend*)> BackendCallback;
+
+  // Runs |callback| with the wrapped Backend on the FILE thread.
+  void RunWithBackend(const BackendCallback& callback) {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+    BrowserThread::PostTask(
+        BrowserThread::FILE, FROM_HERE,
+        base::Bind(
+            &BackendWrapper::RunWithBackendOnFileThread, this, callback));
+  }
+
+  SettingsBackend* GetBackend() const {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+    return backend_;
+  }
+
+ private:
+  friend class base::RefCountedThreadSafe<BackendWrapper>;
+
+  BackendWrapper() : backend_(NULL) {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  }
+
+  virtual ~BackendWrapper() {
+    if (BrowserThread::CurrentlyOn(BrowserThread::FILE)) {
+      delete backend_;
+    } else if (BrowserThread::CurrentlyOn(BrowserThread::UI)) {
+      BrowserThread::DeleteSoon(BrowserThread::FILE, FROM_HERE, backend_);
+    } else {
+      NOTREACHED();
+    }
+  }
+
+  void InitOnFileThread(
+      const scoped_refptr<SettingsStorageFactory>& storage_factory,
+      const SettingsStorageQuotaEnforcer::Limits& quota,
+      const scoped_refptr<SettingsObserverList>& observers,
+      const FilePath& path) {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+    DCHECK(!backend_);
+    backend_ = new SettingsBackend(storage_factory, path, quota, observers);
+  }
+
+  void RunWithBackendOnFileThread(const BackendCallback& callback) {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+    DCHECK(backend_);
+    callback.Run(backend_);
+  }
+
+  // Wrapped Backend. Used exclusively on the FILE thread, and is created on
+  // the FILE thread in InitOnFileThread.
+  SettingsBackend* backend_;
+
+  DISALLOW_COPY_AND_ASSIGN(BackendWrapper);
+};
+
+SettingsStorageFrontend::SettingsStorageFrontend(
+    settings_namespace::Namespace settings_namespace,
+    const scoped_refptr<SettingsStorageFactory>& factory,
+    const SettingsStorageQuotaEnforcer::Limits& quota,
+    const scoped_refptr<SettingsObserverList>& observers,
+    const FilePath& profile_path)
+    : settings_namespace_(settings_namespace) {
+  DCHECK(settings_namespace_ == settings_namespace::LOCAL ||
+         settings_namespace_ == settings_namespace::SYNC);
+  const bool local = settings_namespace_ == settings_namespace::LOCAL;
+  const FilePath app_path = profile_path.AppendASCII(
+      local ? ExtensionService::kLocalAppSettingsDirectoryName
+            : ExtensionService::kSyncAppSettingsDirectoryName);
+  const FilePath extension_path = profile_path.AppendASCII(
+      local ? ExtensionService::kLocalExtensionSettingsDirectoryName
+            : ExtensionService::kSyncExtensionSettingsDirectoryName);
+  app_backend_ =
+      BackendWrapper::CreateAndInit(factory, quota, observers, app_path);
+  extension_backend_ =
+      BackendWrapper::CreateAndInit(factory, quota, observers, extension_path);
+}
+
+SettingsStorageFrontend::~SettingsStorageFrontend() {}
+
+void SettingsStorageFrontend::RunWithStorage(const Extension* extension,
+                                             const StorageCallback& callback) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  // A neat way to implement unlimited storage; if the extension has the
+  // unlimited storage permission, force through all calls to Set() (in the
+  // same way that writes from sync ignore quota).
+  // But only if it's local storage (bad stuff would happen if sync'ed
+  // storage is allowed to be unlimited).
+  bool is_unlimited =
+      settings_namespace_ == settings_namespace::LOCAL &&
+      extension->HasAPIPermission(APIPermission::kUnlimitedStorage);
+
+  scoped_refptr<BackendWrapper> backend =
+      extension->is_app() ? app_backend_ : extension_backend_;
+
+  backend->RunWithBackend(
+      base::Bind(
+          is_unlimited ? &CallbackWithUnlimitedStorage : &CallbackWithStorage,
+          extension->id(),
+          callback));
+}
+
+void SettingsStorageFrontend::DeleteStorageSoon(
+    const std::string& extension_id) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  BackendWrapper::BackendCallback callback =
+      base::Bind(&DeleteStorageOnFileThread, extension_id);
+  app_backend_->RunWithBackend(callback);
+  extension_backend_->RunWithBackend(callback);
+}
+
+SettingsBackend* SettingsStorageFrontend::GetAppBackend() const {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  return app_backend_->GetBackend();
+}
+
+SettingsBackend* SettingsStorageFrontend::GetExtensionBackend() const {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  return extension_backend_->GetBackend();
+}
+
+}  // namespace extensions