conversations-classic/src/main/res/drawable/search_background_dark.xml

<?xml version="1.0" encoding="utf-8"?>
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<layer-list xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:drawable="@color/grey900"/>

    <item>
        <bitmap
            android:alpha="@dimen/background_image_opacity"
            android:gravity="center"
            android:src="@drawable/ic_search_background_white"/>
    </item>
</layer-list>