Pass on download or installation errors from WebstoreInstaller to the CompleteInstall function.

chrome/browser/extensions/api/webstore_private/webstore_private_api.h

 // Copyright (c) 2012 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_API_WEBSTORE_PRIVATE_WEBSTORE_PRIVATE_API_H_
 #define CHROME_BROWSER_EXTENSIONS_API_WEBSTORE_PRIVATE_WEBSTORE_PRIVATE_API_H_
 
 #include <string>
 
 #include "chrome/browser/extensions/bundle_installer.h"
@@ skipping 131 matching lines @@
   SkBitmap icon_;
 
   // A dummy Extension object we create for the purposes of using
   // ExtensionInstallPrompt to prompt for confirmation of the install.
   scoped_refptr<extensions::Extension> dummy_extension_;
 
   // The class that displays the install prompt.
   scoped_ptr<ExtensionInstallPrompt> install_prompt_;
 };
 
-class CompleteInstallFunction : public SyncExtensionFunction {
+class CompleteInstallFunction
+    : public AsyncExtensionFunction,
+      public WebstoreInstaller::Delegate {
  public:
   DECLARE_EXTENSION_FUNCTION_NAME("webstorePrivate.completeInstall");
 
+  // WebstoreInstaller::Delegate:
+  virtual void OnExtensionInstallSuccess(const std::string& id) OVERRIDE;
+  virtual void OnExtensionInstallFailure(const std::string& id,
+                                         const std::string& error) OVERRIDE;
  protected:
   virtual ~CompleteInstallFunction() {}
 
   // ExtensionFunction:
   virtual bool RunImpl() OVERRIDE;
 };
 
 class GetBrowserLoginFunction : public SyncExtensionFunction {
  public:
   DECLARE_EXTENSION_FUNCTION_NAME("webstorePrivate.getBrowserLogin");
@@ skipping 43 matching lines @@
 
  private:
   void CreateResult(bool webgl_allowed);
 
   scoped_refptr<GPUFeatureChecker> feature_checker_;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_WEBSTORE_PRIVATE_WEBSTORE_PRIVATE_API_H_