问CollapsingToolbarLayout安卓中的多行扩展标题？

EN

<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/main_content"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/white"
    android:fitsSystemWindows="true">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="@dimen/detail_backdrop_height"
        android:fitsSystemWindows="true"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">


        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/collapsing_toolbar"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fitsSystemWindows="true"
            app:contentScrim="?attr/colorPrimary"
            app:expandedTitleMarginEnd="16dp"
            app:expandedTitleMarginStart="16dp"
            app:expandedTitleTextAppearance="@style/HeaderTitleStyle"
            app:layout_scrollFlags="scroll|exitUntilCollapsed">


                    <ImageView
                        android:id="@+id/cover_image"
                        android:layout_width="match_parent"                             android:layout_height="@dimen/detail_backdrop_height"
                        android:background="@color/white"
                        android:fitsSystemWindows="true"
                        android:scaleType="fitXY"
                        android:src="@drawable/default_clg_image"
                        app:layout_collapseMode="parallax" />


            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                app:layout_collapseMode="pin"
                app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

        </android.support.design.widget.CollapsingToolbarLayout>
    </android.support.design.widget.AppBarLayout>
</android.support.design.widget.CoordinatorLayout>

app:expandedTitleTextAppearance="@style/HeaderTitleStyle"

<style name="HeaderTitleStyle" parent="@android:style/TextAppearance">
    <item name="android:textColor">#FFFFFF</item>
    <item name="android:textSize">20sp</item>
    <item name="android:singleLine">false</item>
</style>