Prevent duplicate concurrent installs of the same extension

chrome/browser/extensions/active_install_data.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 "chrome/browser/extensions/active_install_data.h"
+
+#include "chrome/browser/extensions/install_tracker.h"
+#include "chrome/browser/profiles/profile.h"
+
+namespace extensions {
+
+// ActiveInstallData:
+
+ActiveInstallData::ActiveInstallData()
+    : percent_downloaded(0), is_ephemeral(false) {
+}
+
+ActiveInstallData::ActiveInstallData(const std::string& extension_id)
+    : extension_id(extension_id), percent_downloaded(0), is_ephemeral(false) {
+}
+
+// ScopedActiveInstall:
+
+ScopedActiveInstall::ScopedActiveInstall(Profile* profile,
+                                         const ActiveInstallData& install_data)
+    : profile_(profile), extension_id_(install_data.extension_id) {
+  DCHECK(profile);
+  DCHECK(!install_data.extension_id.empty());
+
+  InstallTracker* tracker = InstallTracker::Get(profile);
+  DCHECK(tracker);
+  tracker->AddActiveInstall(install_data);
+}
+
+ScopedActiveInstall::ScopedActiveInstall(Profile* profile,
+                                         const std::string& extension_id)
+    : profile_(profile), extension_id_(extension_id) {
+  DCHECK(profile);
+  DCHECK(!extension_id.empty());
+}
+
+ScopedActiveInstall::~ScopedActiveInstall() {
+  if (!extension_id_.empty()) {
+    InstallTracker* tracker = InstallTracker::Get(profile_);

[asargent_no_longer_on_chrome, 2014/07/17 06:24:51]

I'm a little concerned about this class holding a pointer to a Profile - it
seems like it might be possible for us to accidentally hold on to the Profile*
past its destruction during profile shutdown.  What do you think about one of
these alternatives to holding a Profile*?

A) Hold a WeakPtr to the InstallTracker (look it up from the Profile* inside the
ScopedActiveInstall constructor)

or

B) Hold a naked pointer to the InstallTracker, and have some sort of
InstallTrackerShutdownObserver interface that this object implements so that it
can register itself with the InstallTracker and at shutdown time the
InstallTracker can call a method in the interface that tells clients "I'm going
away now; you should drop your pointer to me now". I guess this is sort of
equivalent to a hand-rolled WeakPtr. 

+    DCHECK(tracker);
+    tracker->RemoveActiveInstall(extension_id_);
+  }
+}
+
+void ScopedActiveInstall::CancelDeregister() {
+  extension_id_.clear();
+}
+
+}  // namespace extensions