ReactSlider extends AppCompatSeekBar (#23304)

Summary:
Google recommends to use AppCompat widgets, and this PR changes ReactSlider to extend AppCompatSeekBar.

[Android] [Changed] - ReactSlider extends AppCompatSeekBar
Pull Request resolved: facebook/react-native#23304

Differential Revision: D13973636

Pulled By: cpojer

fbshipit-source-id: 9aa160b186fcea593224c5760a2de0fc3a2b6f85

ReactSlider.java

@@ -8,8 +8,8 @@
 
 import android.content.Context;
 import android.os.Build;
+import android.support.v7.widget.AppCompatSeekBar;
 import android.util.AttributeSet;
-import android.widget.SeekBar;
 import javax.annotation.Nullable;
 
 /**
@@ -20,7 +20,7 @@
  *
  * <p>Note that the slider is _not_ a controlled component (setValue isn't called during dragging).
  */
-public class ReactSlider extends SeekBar {
+public class ReactSlider extends AppCompatSeekBar {
 
   /**
    * If step is 0 (unset) we default to this total number of steps. Don't use 100 which leads to