extensions: Abstract out install delay strategy

chrome/browser/extensions/update_install_gate.cc

Index: chrome/browser/extensions/update_install_gate.cc
diff --git a/chrome/browser/extensions/update_install_gate.cc b/chrome/browser/extensions/update_install_gate.cc
new file mode 100644
index 0000000000000000000000000000000000000000..14173a88cc82de380469ff14df46500b1a8841d5
--- /dev/null
+++ b/chrome/browser/extensions/update_install_gate.cc
@@ -0,0 +1,53 @@
+// Copyright 2016 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/update_install_gate.h"
+
+#include "chrome/browser/extensions/extension_service.h"
+#include "chrome/browser/extensions/extension_util.h"
+#include "chrome/browser/profiles/profile.h"
+#include "extensions/browser/event_router.h"
+#include "extensions/common/extension.h"
+#include "extensions/common/manifest_handlers/background_info.h"
+
+namespace extensions {
+
+UpdateInstallGate::UpdateInstallGate(ExtensionService* service)
+    : service_(service) {}
+
+InstallGate::Action UpdateInstallGate::ShouldDelay(const Extension* extension,
+                                                   bool install_immediately) {
+  // Allow installation when |install_immediately| is set or ExtensionService
+  // is not ready. UpdateInstallGate blocks update when the old version of
+  // the extension is not idle (i.e. in use). When ExtensionService is not
+  // ready, the old version is definitely idle, so the installation is allowed
+  // to proceeded. This essentially allows the delayed installation to happen
+  // during the initialization of ExtensionService.
+  if (install_immediately || !service_->is_ready())
+    return INSTALL;
+
+  const Extension* old = service_->GetInstalledExtension(extension->id());
+  // If there is no old extension, this is not an update, so don't delay.
+  if (!old)
+    return INSTALL;
+
+  if (extensions::BackgroundInfo::HasPersistentBackgroundPage(old)) {
+    const char kOnUpdateAvailableEvent[] = "runtime.onUpdateAvailable";
+    // Delay installation if the extension listens for the onUpdateAvailable
+    // event.
+    return extensions::EventRouter::Get(service_->profile())
+                   ->ExtensionHasEventListener(extension->id(),
+                                               kOnUpdateAvailableEvent)
+               ? DELAY
+               : INSTALL;
+  } else {
+    // Delay installation if the extension is not idle.
+    return !extensions::util::IsExtensionIdle(extension->id(),
+                                              service_->profile())
+               ? DELAY
+               : INSTALL;
+  }
+}
+
+}  // namespace extensions