Prevent duplicate concurrent installs of the same extension

chrome/browser/extensions/active_install_data.h

Index: chrome/browser/extensions/active_install_data.h
diff --git a/chrome/browser/extensions/active_install_data.h b/chrome/browser/extensions/active_install_data.h
new file mode 100644
index 0000000000000000000000000000000000000000..e8c04a2c992855133217d765960bbac740e5ce8e
--- /dev/null
+++ b/chrome/browser/extensions/active_install_data.h
@@ -0,0 +1,65 @@
+// 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.
+
+#ifndef CHROME_BROWSER_EXTENSIONS_ACTIVE_INSTALL_DATA_H_
+#define CHROME_BROWSER_EXTENSIONS_ACTIVE_INSTALL_DATA_H_
+
+#include <string>
+
+#include "base/macros.h"
+#include "base/scoped_observer.h"
+#include "chrome/browser/extensions/install_observer.h"
+
+class Profile;
+
+namespace extensions {
+
+class InstallTracker;
+
+// Details of an active extension install.
+struct ActiveInstallData {
+ public:
+  ActiveInstallData();
+  explicit ActiveInstallData(const std::string& extension_id);
+
+  std::string extension_id;
+  int percent_downloaded;
+  bool is_ephemeral;
+};
+
+// Registers and deregisters and an active extension install with the
+// InstallTracker.
+class ScopedActiveInstall : public InstallObserver {
+ public:
+  // This constructor registers an active install with the InstallTracker.
+  ScopedActiveInstall(InstallTracker* tracker,
+                      const ActiveInstallData& install_data);
+
+  // This constructor does not register an active install. The extension install
+  // is still deregistered upon destruction.
+  ScopedActiveInstall(InstallTracker* tracker, const std::string& extension_id);
+
+  virtual ~ScopedActiveInstall();
+
+  // Ensures that the active install is not deregistered upon destruction. This
+  // may be necessary if the extension install outlives the lifetime of this
+  // instance.
+  void CancelDeregister();
+
+ private:
+  void Init();
+
+  // InstallObserver implementation.
+  virtual void OnShutdown() OVERRIDE;
+
+  InstallTracker* tracker_;
+  ScopedObserver<InstallTracker, InstallObserver> tracker_observer_;
+  std::string extension_id_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedActiveInstall);
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_ACTIVE_INSTALL_DATA_H_