Create CrxInstaller directly in WebstoreInstaller

chrome/browser/download/download_crx_util.h

Index: chrome/browser/download/download_crx_util.h
diff --git a/chrome/browser/download/download_crx_util.h b/chrome/browser/download/download_crx_util.h
index 1807a59b7abbf053b971e72a4279d5afb769eb79..cc99c1956c8dfc8c2208e9d28b6cf4b659aaee5d 100644
--- a/chrome/browser/download/download_crx_util.h
+++ b/chrome/browser/download/download_crx_util.h
@@ -30,6 +30,11 @@ namespace download_crx_util {
 void SetMockInstallPromptForTesting(
     scoped_ptr<ExtensionInstallPrompt> mock_prompt);
 
+// Create and pre-configure a CrxInstaller for a given |download_item|.
+scoped_refptr<extensions::CrxInstaller> CreateCrxInstaller(
+    Profile* profile,
+    const content::DownloadItem& download_item);
+
 // Start installing a downloaded item item as a CRX (extension, theme, app,
 // ...).  The installer does work on the file thread, so the installation
 // is not complete when this function returns.  Returns the object managing