Fix a crash during installing an extension with shared modules.

BUG=383310

Review URL: https://codereview.chromium.org/334633003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@276876 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/extensions/webstore_installer.cc

@@ -489,7 +489,9 @@ void WebstoreInstaller::OnDownloadStarted(
 }
 
 void WebstoreInstaller::OnDownloadUpdated(DownloadItem* download) {
-  CHECK_EQ(download_item_, download);
+  // DownloadItemImpl calls the observer for a completed item, ignore it.
+  if (download_item_ != download)
+    return;
 
   switch (download->GetState()) {
     case DownloadItem::CANCELLED: