I received this message because I used the following method to override styles for different API levels:
<style name="ToolBar" parent="ToolBar.Base"/>
<style name="ToolBar.Base">
<item name="android:layout_width">match_parent</item>
<item name="android:layout_height">?actionBarSize</item>
<item name="android:background">@color/primary</item>
</style>
And then adding
<style name="ToolBar" parent="ToolBar.Base">
<item name="android:elevation">4dp</item>
</style>
v21/styles. ToolBar , . - , . , , , Android .
, ToolBar.Base ToolBar_Base .