Unrevert: Show the install dialog for the initial load of an unpacked extension
with plugins.

First landing broke some browser tests.

BUG=83273
TEST=in the extensions managmenet page, with developer mode enabled, Load an unpacked extension on an extension with NPAPI plugins. You should get an install dialog.
TBR=mihaip

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@87738 0039d316-1c4b-4281-b951-d872f2087c98
void ExtensionService::SetBackgroundPageReady(const Extension* extension) {
  DCHECK(!extension->background_url().is_empty());
  extension_runtime_data_[extension->id()].background_page_ready = true;
  NotificationService::current()->Notify(
      NotificationType::EXTENSION_BACKGROUND_PAGE_READY,
      Source<const Extension>(extension),
      NotificationService::NoDetails());
}

void ExtensionService::SetBackgroundPageReady(const Extension* extension) {
  DCHECK(!extension->background_url().is_empty());
  extension_runtime_data_[extension->id()].background_page_ready = true;
  NotificationService::current()->Notify(
      NotificationType::EXTENSION_BACKGROUND_PAGE_READY,
      Source<const Extension>(extension),
      NotificationService::NoDetails());
}
