private void prepareActionButton(CustomTabsIntent.Builder builder) {
        // An example intent that sends an email.
        Intent actionIntent = new Intent(Intent.ACTION_SEND);
        actionIntent.setType("*/*");
        actionIntent.putExtra(Intent.EXTRA_EMAIL, "example@example.com");
        actionIntent.putExtra(Intent.EXTRA_SUBJECT, "example");
        PendingIntent pi = PendingIntent.getActivity(this, 0, actionIntent, 0);
        Bitmap icon = BitmapFactory.decodeResource(getResources(), R.drawable.ic_share);
        builder.setActionButton(icon, "send email", pi, true);
    }
Once per second, asks the framework for the process importance, and logs any change.
Application/src/main/java/org/chromium/customtabsclient/MainActivity.java