[Extensions] Migrate ExtensionInstallPrompt::Delegate to be a callback

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

Index: chrome/browser/extensions/api/webstore_private/webstore_private_api.h
diff --git a/chrome/browser/extensions/api/webstore_private/webstore_private_api.h b/chrome/browser/extensions/api/webstore_private/webstore_private_api.h
index 457a18fffda5203c076e99f7eebcd7128e336fca..91a94b6022f01a40bad072e6acfb0d49763f6a77 100644
--- a/chrome/browser/extensions/api/webstore_private/webstore_private_api.h
+++ b/chrome/browser/extensions/api/webstore_private/webstore_private_api.h
@@ -46,7 +46,6 @@ class WebstorePrivateApi {
 
 class WebstorePrivateBeginInstallWithManifest3Function
     : public UIThreadExtensionFunction,
-      public ExtensionInstallPrompt::Delegate,
       public WebstoreInstallHelper::Delegate {
  public:
   DECLARE_EXTENSION_FUNCTION("webstorePrivate.beginInstallWithManifest3",
@@ -70,9 +69,10 @@ class WebstorePrivateBeginInstallWithManifest3Function
                               InstallHelperResultCode result,
                               const std::string& error_message) override;
 
-  // ExtensionInstallPrompt::Delegate:
-  void InstallUIProceed() override;
-  void InstallUIAbort(bool user_initiated) override;
+  void OnInstallPromptDone(ExtensionInstallPrompt::Result result);
+
+  void HandleInstallProceed();
+  void HandleInstallAbort(bool user_initiated);
 
   ExtensionFunction::ResponseValue BuildResponse(
       api::webstore_private::Result result,