ExtensionDelegate to abstract extension implementation

athena/extensions/extension_delegate_impl.cc

+// Copyright 2014 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 "athena/extensions/public/extension_delegate.h"
+#include "base/macros.h"
+#include "extensions/common/extension_set.h"
+#include "extensions/shell/browser/shell_extension_system.h"
+
+namespace athena {
+namespace {
+
+ExtensionDelegate* instance = NULL;
+
+class ShellExtensionDelegate : public ExtensionDelegate {
+ public:
+  explicit ShellExtensionDelegate(content::BrowserContext* context)
+      : context_(context),
+        extension_system_(
+            static_cast<extensions::ShellExtensionSystem*>(
+                extensions::ExtensionSystem::Get(context))) {
+    if (extension_system_->extension())

[Yoyo Zhou, 2014/08/20 20:37:27]

I know in the current implementation the extension doesn't change, but this
seems a little bit fragile. Why not build the ExtensionSet on demand when we
call GetExtensionSet?

[oshima, 2014/08/20 21:39:21]

Done.

+      shell_extensions_.Insert(extension_system_->extension());
+  }
+  virtual ~ShellExtensionDelegate() {

[Yoyo Zhou, 2014/08/20 20:37:27]

nit: line breaks between function definitions

[oshima, 2014/08/20 21:39:21]

Done.

+  }
+
+ private:
+  // ExtensionDelegate:
+  virtual content::BrowserContext* GetBrowserContext() const OVERRIDE {
+    return context_;
+  }
+  virtual extensions::ExtensionSet* GetExtensionSet() OVERRIDE {
+    return &shell_extensions_;
+  }
+  virtual void Launch(const std::string& id) OVERRIDE {
+    extension_system_->LaunchApp();
+  }
+
+  content::BrowserContext* context_;
+  extensions::ShellExtensionSystem* extension_system_;
+  extensions::ExtensionSet shell_extensions_;
+
+  DISALLOW_COPY_AND_ASSIGN(ShellExtensionDelegate);
+};
+
+}  // namespace
+
+ExtensionDelegate::ExtensionDelegate() {
+  DCHECK(!instance);
+  instance = this;
+}
+
+ExtensionDelegate::~ExtensionDelegate() {
+  DCHECK(instance);
+  instance = NULL;
+}
+
+// static
+ExtensionDelegate* ExtensionDelegate::Get(content::BrowserContext* context) {
+  DCHECK(instance);
+  DCHECK_EQ(context, instance->GetBrowserContext());
+  return instance;
+}
+
+// static
+void ExtensionDelegate::Shutdown() {
+  DCHECK(instance);
+  delete instance;
+}
+
+// static
+void ExtensionDelegate::InitExtensionDelegateForShell(
+    content::BrowserContext* context) {
+  new ShellExtensionDelegate(context);
+}
+
+}  // namespace athena