Add an option to turn off hiding controls during ads

Issue: #3532

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=178372763

RELEASENOTES.md

@@ -45,6 +45,8 @@
   * Skip ads before the ad preceding the player's initial seek position
     ([#3527](https://github.com/google/ExoPlayer/issues/3527)).
   * Fix ad loading when there is no preroll.
+  * Add an option to turn off hiding controls during ad playback
+    ([#3532](https://github.com/google/ExoPlayer/issues/3532)).
 
 ### 2.6.0 ###
 

library/ui/src/main/res/values/attrs.xml

@@ -47,6 +47,7 @@
     <attr name="default_artwork" format="reference"/>
     <attr name="use_controller" format="boolean"/>
     <attr name="hide_on_touch" format="boolean"/>
+    <attr name="hide_during_ads" format="boolean"/>
     <attr name="auto_show" format="boolean"/>
     <attr name="resize_mode"/>
     <attr name="surface_type"/>