Trigger app banner when add to homescreen is pressed and WebAPKs are enabled.

chrome/browser/android/banners/app_banner_manager_android.h

Index: chrome/browser/android/banners/app_banner_manager_android.h
diff --git a/chrome/browser/android/banners/app_banner_manager_android.h b/chrome/browser/android/banners/app_banner_manager_android.h
index 541501aa9b7d7856e11c54aa11d9a64bc7851d1c..4d5bf7e5e3d57cc18b84d9f84cc241af5ded4630 100644
--- a/chrome/browser/android/banners/app_banner_manager_android.h
+++ b/chrome/browser/android/banners/app_banner_manager_android.h
@@ -11,6 +11,8 @@
 #include "chrome/browser/banners/app_banner_manager.h"
 #include "content/public/browser/web_contents_user_data.h"
 
+struct ShortcutInfo;
+
 namespace banners {
 
 // Extends the AppBannerManager to support native Android apps.
@@ -97,6 +99,9 @@ class AppBannerManagerAndroid
                           const GURL& url,
                           const std::string& id);
 
+  // Create shortcut info from the Web Manifest for a web app.
+  std::unique_ptr<ShortcutInfo> CreateShortcutInfo();
+
   // The Java-side AppBannerManager.
   base::android::ScopedJavaGlobalRef<jobject> java_banner_manager_;