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

chrome/browser/ui/android/infobars/app_banner_infobar_android.cc

Index: chrome/browser/ui/android/infobars/app_banner_infobar_android.cc
diff --git a/chrome/browser/ui/android/infobars/app_banner_infobar_android.cc b/chrome/browser/ui/android/infobars/app_banner_infobar_android.cc
index cf9e8539ea5006ccc89a3c6b0cd11d5d4e1b007a..f017ba9215b9e4825cc9fa77d4ae7a0435298556 100644
--- a/chrome/browser/ui/android/infobars/app_banner_infobar_android.cc
+++ b/chrome/browser/ui/android/infobars/app_banner_infobar_android.cc
@@ -73,3 +73,8 @@ void AppBannerInfoBarAndroid::OnInstallStateChanged(int new_state) {
                                                      new_state);
 }
 
+void AppBannerInfoBarAndroid::InstallWebApk(
+    content::WebContents* web_contents) {
+  static_cast<banners::AppBannerInfoBarDelegateAndroid*>(GetDelegate())
+      ->InstallWebApk(web_contents);
+}