Update PlayerView javadoc

Added a note about using TextureView only on hardware accelerated window.

Issue: #3901

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=187498594

library/ui/src/main/java/com/google/android/exoplayer2/ui/PlayerView.java

@@ -111,7 +111,9 @@ import java.util.List;
  *   <li><b>{@code surface_type}</b> - The type of surface view used for video playbacks. Valid
  *   <li><b>{@code surface_type}</b> - The type of surface view used for video playbacks. Valid
  *       values are {@code surface_view}, {@code texture_view} and {@code none}. Using {@code none}
  *       values are {@code surface_view}, {@code texture_view} and {@code none}. Using {@code none}
  *       is recommended for audio only applications, since creating the surface can be expensive.
  *       is recommended for audio only applications, since creating the surface can be expensive.
- *       Using {@code surface_view} is recommended for video applications.
+ *       Using {@code surface_view} is recommended for video applications. Note, TextureView can
+ *       only be used in a hardware accelerated window. When rendered in software, TextureView will
+ *       draw nothing.
  *       <ul>
  *       <ul>
  *         <li>Corresponding method: None
  *         <li>Corresponding method: None
  *         <li>Default: {@code surface_view}
  *         <li>Default: {@code surface_view}