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

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

Index: chrome/browser/ui/android/infobars/app_banner_infobar_android.h
diff --git a/chrome/browser/ui/android/infobars/app_banner_infobar_android.h b/chrome/browser/ui/android/infobars/app_banner_infobar_android.h
index 0ace22c5f66c5ea60afddb531bc92ca31f43dc52..8ebbc0245b96751ee81309da67402e89902e1f70 100644
--- a/chrome/browser/ui/android/infobars/app_banner_infobar_android.h
+++ b/chrome/browser/ui/android/infobars/app_banner_infobar_android.h
@@ -35,6 +35,12 @@ class AppBannerInfoBarAndroid : public ConfirmInfoBar {
   // that may have been disabled.
   void OnInstallStateChanged(int new_state);
 
+  // Called when user clicks the "Add To Homescreen" from the app menu to
+  // install a WebAPK. The banner skips the state of showing "Add To
+  // Homescreen" on the button and jumps to the state of showing "Adding"
+  // and starts the installation.
+  void InstallWebApk(content::WebContents* web_contents);

[gone, 2016/08/31 18:12:46]

I don't think this function belongs here because it's a functional change.  It
even calls through directly to the delegate.  Why don't you just call it on the
delegate from AddToHomeScreenManager::CreateInfobar?  You already have access to
it there.

[Xi Han, 2016/08/31 20:11:48]

Hmm, this call needs to be made after both AppBannerInfobarDelegateAndroid and
AppBannerInfobarAndroid are initialized on Java and C++ sides. This is because
the InstallWebAPK() not only starts the installation, but also updates the texts
on the app banner infobar. However, in CreateInfoBarForWebAPK(), the delegate is
a unique_ptr, and it becomes invalid as long as the infobar is created. So I
can't call InstallWebAPK directly through the delegate, but via infobar and to
the delegate. Beside, I don't want add more hack to the
AppBannerInfobarAndroid.java to make the text is initialized with WebAPK logic
(the "Adding" button). I would like to hear if you have better idea.

[gone, 2016/08/31 20:24:22]

Your change to AppBannerInfoBarAndroid::InstallWebApk() consists only of a call
to delegate()->InstallWebApk(web_contents).  That's called at the very end of
CreateInfobar, where everything has already been built.

Can't you just call

InfoBarDelegate* delegate =
static_cast<AppBannerInfoBarAndroid*>(infobar)->delegate();
static_cast<AppBannerInfoBarDelegate*>(delegate)->InstallWebApk(web_contents);?

[Xi Han, 2016/08/31 20:59:24]

You are right, updated. Thanks:)

+
  private:
   // InfoBarAndroid overrides.
   base::android::ScopedJavaLocalRef<jobject> CreateRenderInfoBar(